All other things equal, probably.

People hiring on freelance sites are looking for the perfect Silicon Valley genius programmer who inexplicably turned down a six figure offer with Facebook to strike out on his own and charge $15/hr for his time on Rentacoder.

They really do expect to find this person, and are therefore shocked to see the candidates that are actually available. They'll naturally try to sift through the heap and find the person closest to their ideal, and, being non-technical, the only thing they really have to go on is writing style.

So the "dear sir look no further we are A++++++ professional company" guys all red-flag themselves out of the competition leaving the one dude in Iowa who bothered to put together a complete sentence.

The takeaway from this is that if you're offshore, the best thing you can do is work on your English. Preferably your casual proposal-writing English, since the half dozen sentences you put together for a bid will likely be the only thing a potential client ever reads. Unless that looks right, it doesn't matter what your technical skills are like. Nobody will ever get around to asking.

It depends. Some US entities are keen to hire US based freelancers, just to be 'more' safe. Others do not care, and hire freelancer with best proposal/price. Also some hire people to make their critical product for pennies, and then complain that the freelancers suck at their work. As for my experience US people mostly care that you will be available during their working hours.

I have seen bias based on operating hours which can benefit USA based freelancers, but rarely I had seen someone explicitly wanting someone from USA when the job didn't involve on-site work.

OTOH, I have actually seen jobs restricted to countries marked as "developing economies" in order to take only the cheaper bids.