True, but in most of the U.S. the number two language isn't all that useful. Also I should add it's not just a matter of utility, it's also a matter of opportunity. I mean sure, if you go looking for speakers of another language you can find them, but it's not ambient. I hear many different languages spoken here in Seattle, but almost all of these speakers speak English well.

Also I should add that I'm not arguing against bilingualism, I'm just saying there are practical reasons why it is not so common here in the U.S.