I was wondering the same thing. Maybe in the USA it is easier due to our relaxed (almost non-existent) business oversight from the government? Not sure.

I don’t know the answer but they pointed this out further in the press release:

However, it’s also important for us that Mastodon is one of the few, if not the only social media platform that operates out of the EU, and we would like to keep it that way.

I’d assume that this is for a reason, too. If it were advantageous to run your company out of the EU people would probably do so sometimes.