Unfortunately US in Y, particularly TATL, is probably not the best experience - I last did it out of PHL a few months before US left Star, and I doubt the AA merger has made much difference.

It may be different on the 330-200, but iirc the seats on the -300 had no headrest, and breakfast consisted of - well, precisely nothing. Not even a cup of tea or coffee. I'm sure half the plane simply assumed they'd missed it because they were asleep.

On the other hand, on the same trip I had possibly one of the best crew members I've ever known on one of the short domestic hops on a non-mainline service - young, but very enthusiastic, clearly enjoying her job and very customer focused (and yes, given it was US I was fairly shocked as well!).

However, I did survive it and am here to tell the tale, so I'm sure you'll be fine .

As others have said, PHL isn't at all a bad airport to connect in, although US' other main hub at CLT has probably the most efficient immigration in the US.