If foreign airlines could operate domestically within the USA, I bet you'd be seeing domestic carriers pleading for new Federal regulation to protect their grimy little routes, sort of how you'd expect to see the US Postal Service flip it's lid if UPS, FedEx, and DHL were allowed to carry first class mail.
Look at what the domestic airlines do to cut costs: unregulated service and maintenance contracts in Latin America, probably using counterfeit Chinese aerospace parts. They cram you in like sardines. All so trailer trash could fly instead of taking the Greyhound bus like they had to back before the early 1980s? Sorry, but I remember what domestic flight was like in the 70s. It was something special. Now look. It's terrible. How can anyone argue?
You know, you disappoint me. If you don’t like dressing “unacceptably” on a flight, then don’t. This is America! If you don’t like something, don’t participate, but don’t expect the government to dictate how I will live just because you don’t like it.