Those are not US-based though, I believe the OP wants to know how to be an FA for a US airline, based in the US. Correct me if I'm wrong...
You can, by becoming one of our truly International cabin crew team.
You will be based in Dubai, a cosmopolitan city that has rapidly grown into a global tourism and commercial centre that offers something to everyone.
They put the cities as LA/NY etc because that is where the recruitment events take place.