Is what you mean whether a US carrier will add premium economy as defined by carriers such as BA (WT+), CX, AF and TG for international flights? If so, then such a cabin does exist on US domestic flights: it's called first class.

Or if you are asking whether a US carrier will add such a cabin (roughly equivalent to US domestic F) for its international flights, then I think there would be a market for it - such as there is for those other airlines' cabins.