20 years ago US-based carriers were crap, which is why you got so many Americans flying using non-US carriers to Europe/Asia etc.
Luckily I’ve not had to go to the states in +10 years but use to go monthly. 99% of the time I’d use BA.
They’re still crap, especially internal flights.
For long haul, I do the US about once a month, on a mix of BA, AA and Delta. BA have by far the best service, food and drinks, and an excellent seat (especially upstairs). AA have OK service and the seats vary, the new reverse herringbone is very good. Delta are friendly, lovely folks, but the seat and food are average at best.
Internally, AA are the only airline to have lost my luggage. Twice. On the exact same flight, two years apart! Skillz. The MDs they fly are noisy old rustbuckets, only saved by the gorgeous bare aluminium body.
I’d rather fly Southwest than Unoted.
Given the choice, for long haul, BA or Cathay every time.