According to The National Association of Investors, just one in three Americans feels "comfortable" investing in foreign stocks or bonds.

That, my friend, spells trouble
If this kind of thinking continues, we could be headed for some serious underperformance, if not worse. Or so says the "smartest man in Europe."

The smartest who in what? I know. That's what I said. But I heard that from Byron Wien. Apparently, this mysterious chap earned his crown by consistently identifying trends that would have major impacts on global financial markets.

He even predicted the collapse of communism and the dismantling of the Berlin Wall, or so the story goes. And yes, he warned us to start looking for investments abroad long before the recent historic bull market in foreign stocks.

You think I've lost my mind, don't you?
In my defense, you can verify this in The Washington Post. And this guy Wien is no hack. He was a top equity analyst at Morgan Stanley for years. So I'm inclined to hear him out. As for his "mystery man" on the ground ... who cares? Just look at the numbers.

In 2005, stock markets in countries as diverse as Egypt, Russia, Turkey, South Korea, and Austria all gained 50% or more -- dwarfing U.S. stocks. The same thing happened in 2006, with China and India leading the charge. And it's happened again in 2007, too. I don't know about you, but I'm starting to sense a trend.

In other words, when it comes to making money overseas, we haven't missed the boat. In fact, when Wien last crossed the Atlantic to consult with his "source," he was more adamant than ever that we move some of our investment capital overseas. For what it's worth, I'm taking him up on it.

"Global is definitely the way to go"
Not ready to gamble your future on some mystery man? Well, how about a Wharton professor? When Dr. Jeremy Siegel met with us here at Fool HQ, those were his exact words -- "definitely the way to go." Siegel insists we should hold as much as 40% of our portfolios in foreign stocks.

I wish I'd listened. I imagine some U.S. fund managers agree. Last year, the popular $4.8 billion Janus Research (JAMRX) fund rode some pretty solid holdings, including big positions in Apple, Qualcomm (NASDAQ:QCOM), and EMC (NYSE:EMC), to a market-trailing 8.7% gain.

But Janus might have fared even worse without its 20% exposure to foreign stocks. After all, too many U.S. stalwarts, from Caterpillar (NYSE:CAT) to Intel (NASDAQ:INTC) and even Amgen (NASDAQ:AMGN), trailed the S&P 500 or, worse, struggled to eke out any gains at all -- and that's to say nothing of the whooping Toyota has put on Ford and General Motors over the past few years.

Born on the Fourth of July
I assure you, I'm not some doomsayer prophesizing the collapse of the West and the rise of "Chindia." I have too much faith in America for that ... and way too much invested in the U.S. market.

But it's also a fact that more than half the capitalization of all public companies already resides overseas. And just last year, investors poured $53 million into foreign large-company funds, up 32% from the year before. And, yes, I'm one of them.

So far, I've settled for index funds -- the iShares EAFE Index and Vanguard Emerging Markets Index. In truth, I've been reluctant to invest overseas on my own. But now I have a mystery man on the ground, too -- a Bill Mann, to be specific.

If you haven't heard of Bill, he's a globetrotter and an expert on international markets. In fact, I traveled with Bill and his team to India and China in June, and he just returned from South America (I'll show you how you can hear what he uncovered).

Need help, too?
You don't have to cross the Atlantic for good advice, either. Bill recently launched an investment newsletter service called Motley Fool Global Gains to help folks like us invest with confidence overseas. Bill's a serious investor, so it's not exactly cheap to join.

But that's what makes this such an interesting proposition: Right now, you can join Global Gains for 30 days and pay nothing. You can sample the complete service, read the latest issue, and hear what Bill discovered on his trip to South America -- and if you don't like it, you don't pay.

Of course, you won't actually go broke if you don't invest overseas. But it could cost you some serious money. Why not take Bill up on his offer and try Global Gains free for a month instead? To learn more, click here.

This article was originally published on Jan. 17, 2007. It has been updated.

Fool contributor Paul Elliott owns shares of the iShares EAFE Index and Vanguard Emerging Markets Index, but no other company mentioned. Intel is a Motley Fool Inside Value pick. The Motley Fool has a disclosure policy.