Here’s my big insight for today: U.S. banks have a big long-term problem.

But not the one you’re thinking of right now. (Yes, I do have secret powers and can tell what you’re thinking—although only about bank stocks.)

The headlines are full of news on robo signers, mortgage foreclosure moratoriums, and put backs that will cost banks billions over the next five years and drag out any resolution of the U.S. mortgage crisis.

But that’s not the biggest problem facing U.S. banks or the one that in the long term will doom them to second-class global status unless they can fix it.

What’s that problem? The big U.S. banks—JPMorgan Chase (JPM), Bank of America (BAC), Wells Fargo (WFC), and Citigroup (C)—are locked out of the fastest growing banking markets in the world (emerging economies especially in Asia) and are locked into some of the slowest growing (the United States and Europe). And I don’t see an easy way in the long term for these U.S. banks to break out of their slow growth trap.

And that—if you agree with the argument I lay out below—should determine how you invest in these stocks, if you invest in them at all.

Let me pick on JPMorgan Chase, the best managed of the big U.S. banks and the one that came through the financial crisis in the best shape, to illustrate the problem.

In its October 13 third quarter earnings report JPMorgan Chase announced disappointing revenue growth. In fact the bank announced a drop in revenue from the third quarter of 2009. Revenue dropped 15.4% from the third quarter a year ago.

Some of this drop in revenue was because of the widely anticipated drop in trading volumes and therefore in trading revenue in the quarter. Revenue from JPMorgan Chase’s investment banking business fell to $5.4 billion, down from $7.5 billion in the third quarter of 2009 and $6.3 billion in the second quarter of 2010.

But let’s look at the rest of the company’s core businesses. In retail financial services revenue fell 7% from the third quarter of 2009. The part of that larger unit called retail banking showed a 3% decline in revenue from the third quarter of 2009. Credit services net revenue fell 18% from that quarter. Mortgage banking net revenue dropped 7%.

Now you can say that these drops in revenue were the result of a slowing U.S. recovery. And that revenue will start to grow again when the U.S. economy comes out of this slump in the recovery in, economists now project, the second half of 2011.

And I’d totally agree. That’s why I think a stock like JPMorgan Chase is a good medium term buy and why I added it to my Jubak Picks on September 16, 2010 with a target price of $55 a share. (To see more on this pick and my entire Jubak’s Picks portfolio go to https://jubakpicks.com/the-jubak-picks/ )

Buying a good U.S. bank stock in anticipation of a stronger U.S. economy in the second half of 2011 is, in my opinion, a good idea.

But that’s just the medium term. Remember I said that U.S. banks have a big long-term problem?

They do. It’s called slow growth in the world’s developed economies where these banks do the bulk of their business. Much slower growth than in the world’s developing economies.

Look at the latest economic projections from the International Monetary Fund (IMF) to get a feel for the growth disparities.

On October 6 the IMF (International Monetary Fund) released its forecast for global economic growth 2010 and 2011. Developed economies are projected to grow by 2.7% this year and 2.2% in 2011. The deceleration will begin in the second half of 2010 and continue into the first half of 2011 before growth picks up again in the second half of 2011. (If the IMF is looking for just 2.2% growth for the entire year, the first half of 2011 could be very rocky indeed.)

The IMF projected that the U.S. economy will grow by 2.6% in 2010 and just 2.2% in 2011. The economies of the Euro Zone will grow by 1.7% in 2010 and 1.5% in 2011.

Developing economies, on the other hand, will growth by 7.1% in 2010 and 6.4% in 2011. China’s growth will slow to 9.6% in 2011 from a projected 10.5% in 2010. India will grow by 9.7% this year, the IMF projects, and 8.4% in 2011.

Add in the contrast between a saturated banking market in the U.S. and a huge unbanked population in the developing world and the gap in relative growth potential gets even larger. McKinsey & Co. estimates a global count of 2.5 billion people who aren’t served by either formal or informal banking institutions. About 2.2 billion of these live in Africa, Asia, Latin America and the Middle East.

Not all of these unbanked will be banking customers any time soon. Many are too poor or live in remote areas, but the figures do give a general feel for the potential in developing economies.

You can get a more precise measure by looking at a financial product such as credit and charge cards. In 2005 in the U.S. credit and charge cards per capita stood at 2.53, according to the U.S. International Trade Administration. That same year in India per capita credit and charge cards were just 0.02 and in Brazil just 0.38. No wonder that consultants RNCOS project compound annual growth in credit and charge card numbers of 12% from 2010 to 2013.

This would seem to be a huge growth opportunity for a bank such as JPMorgan Chase. But 75% of the bank’s revenue now comes from the United States. And getting into many of these emerging markets, especially in Asia, is going to be quite a challenge.

To understand how big a challenge compare JPMorgan Chase with Standard Chartered (SCBFF), a bank with its roots in Asia (despite being headquartered in the United Kingdom) and that derives the majority of its revenue from Asia, Africa, and the Middle East.

JPMorgan Chase likes to boast that it has a Tier 1 capital ratio of 9.5% that will let it easily meet the new Basel III rules.

Standard Chartered has just announced its second rights offering in the last 15 months in order to raise capital. Even though it doesn’t need the capital to meet the Basel III standards for capital. The most recent rights offer will make the bank’s Tier 1 capital ratio to 12.6%.

So why is Standard Chartered raising this money? Because the bank knows that the price of doing business is much of Asia is a capital ratio that’s higher now than the Basel III rules will require by 2018. Regulators and institutions in these markets expect banks to have 10%, 11% and even 12% Tier 1 capital ratios. So think of the Standard Chartered rights offerings as the price of admission to these emerging markets. (Yes, it does take some rethinking of assumptions if you’re an investor from a developed economy and you’re used to assuming that developed economies must have tougher financial standards.)

And beyond the price of admission, raising this much capital means that Standard Chartered will be able to meet capital requirements even while it expands its balance sheet. (That’s banker speak for “grow.”) Many developed economy banks are raising their capital ratios by shrinking their balance sheets. In other words they’re raising their capital ratios not be adding more capital to the top of the fraction but by subtracting assets (loans, for example) from the bottom of the fraction.

That’s not a formula for growth, I might note.

So can’t JPMorgan Chase or any other developed market bank, raise the capital it needs as the price of entry. Sure. But it’s going to be very expensive.

You see U.S. banks, even a good one such as JPMorgan Chase, aren’t as profitable as many of the banks that have already tapped into emerging market growth. JPMorgan Chase, and remember this is a well-run U.S bank, earned a return on equity of 8.73% during the last 12 months, according to Morningstar. Standard Chartered earned 12.73% during the same period.

Raise a dollar of capital through an offering of shares and get roughly 50% higher returns. That’s a recipe for raising capital in the financial markets at a much lower cost.

It’s also one reason that JPMorgan Chase sells at 9.97 times trailing 12-month earnings per share and Standard Chartered sells for 18.23 times trailing earnings.

That huge gap in profitability suggests that the only way for a JPMorgan Chase to catch a Standard Chartered in the world’s new growth markets is to buy it—or a bank like it that already has a huge presence in these markets. And would be very expensive

Which suggests another way to look at what bank stocks you want to own for the long-term.

Either buy the shares of the developed economy banks that already own a big piece of the developing economy banking market and are positioned for growth in those markets because of their history and their profitability. On that list I’d put Standard Chartered, Banco Santander (STD), and HSBC (HBC). (Of course, you can also buy the local developing market banking leaders such as Brazil’s Itau Unibanco (ITUB) or Banco Bradesco (BBD) or India’s HDFC Bank (HDB).)

Or buy the shares of banks with a big presence in developing economies that, for one reason or another, aren’t so very expensive. The one that comes to mind here is Citigroup (C), once one of top franchises in developing economies. The bank still has a tremendous banking network and very high name recognition in these economies. And it sells for a market cap of just $120 billion. That’s a fair hunk of cash but still well short of the $150 billion market cap of JPMorgan Chase.

And the nice thing is that while you wait for somebody to decide that the best way to buy into the developing economies is by buying Citigroup, in the mid-term you’ve got a good chance of making a profit on the recovery in the U.S. economy in the second half of 2011.

Maybe the only thing Citigroup doesn’t have going for it is a good chance to produce a positive return for an investor in the near term—say, the next six months—if the U.S. economy continues to weaken.

But then you could say that about any U.S. bank in the near term, couldn’t you?

Full disclosure: I don’t own shares of any company mentioned in this post in my personal portfolio.