Until now, most average investors were pretty much restricted to owning mutual funds or electronically traded funds — commonly known as ETFs — with stocks from a particular market. Most retail investors have shied away from owning foreign stocks because there isn't as much research available to them, while funds tend to spread the risk.

There's a growing consensus on Wall Street that investors should diversify overseas, appropriating 25 percent of their portfolio to foreign investments. More and more Americans are sinking cash into mutual funds outside the U.S., where last year saw broad advances.

For example, funds that tracked the Asia-Pacific region — excluding Japan — had a 29.61 percent return last year, according to Lipper. Latin American funds jumped 43.73 percent, while those tracking China returned a staggering 61.51 percent in 2006.

Lilien believes the timing is now right where investors are becoming more interested in buying stocks outside of the U.S. E-Trade tinkered with the idea of offering cross-border training off and on during since 1999, he said.

However, the demand just wasn't there after the dot-com bubble burst in 2001. Wall Street meandered before steadily moving higher in the past four years.

"It was only a matter of time when the U.S. investor became interested and ready for global stock trading," Lilien said. "International is a fundamental part of everyone's portfolio, and I don't think that's going to change."