MtGox's willingness to be regulated under strict structuring laws is a clear indication that they are very legit; therefore, they have nothing to fear anything from the US government. I don't see anything wrong with it. MtGox is regulated in Japan. It's not some shady 3rd-world country there. It's Japan. They have real office you can walk to. MtGox people are not anonymous. They have posted photos of themselves working in the office.
MtGox is not the problem that's happening to Bitcoin right now. Heck, today's price slump is probably just a coordinated attack by big holders so that they could get more cheaper coins. That's the tactics they got so many BTCs the first place.