Ah, of course. Only in the US. For a change it would be nice if they started literally anywhere else.
Europe has too many languages. China requires you to give up 50% or more of your company for the "privilege" of doing business there, plus you must deal with censorship with respect to the type of content your game(s) can include. India has an extremely heavy tax burden. Japan and Korea are too small. Latin America, as a whole, is generally a rounding error in terms of video game sales, for various reasons.
The U.S. is the only place where it makes sense to launch. Especially when you're a U.S. company, with U.S. employees.