Spoken like a true underdog. To be threatened by something you have to care about it, and I think most Americans simply don't care about soccer.
I mean threat in the sense that the first thing most critics cite right off the bat is comparing it to whatever their sport of choice is be it baseball, football, skeet shooting, or whatever as if trying to make the sport sound "inferior" which it quite isn't. It's popularity "worldwide" speaks for itself compared to it's popularity on our little red, white, and blue land mass. If they really didn't care, they wouldn't be coming out and speaking for or against it. By the response here, people obviously care one way or another.
As for "the boom is coming" - that's what Linux guys keep saying about the Linux Desktop, and have been for as long as Windows has remained dominant.
I apologize, I know nothing about that.
Variety is great and everyone is entitled to their own preferences, but Soccer, like the Linux Desktop, is nothing more than a niche with a strong minority (in the numerical sense) fanbase. It isn't and probably won't be a mainstream spectator sport in this country any time soon, if ever. But look on the bright side... at least you're not as bad as NASCAR
I wouldn't call majority of the world a "niche." If anything, it is the U.S. that is the odd man out in terms of soccer.