America has a population that dwarfs both countries, so it has a larger pool of people to draw from. On top of thar, entertainment is one of our biggest exports, and everyone knows the industry is bigger here, and very well-funded.

That said, I feel like British TV is just more classic and classier. They do less gimmicky shit and stick to raw talent and great fucking writing.

I can't speak to Australian TV because I haven't seen any.

I would try to think less about who is the best and more about enjoying both US and British TV for their strengths. Foreign TV and movies in general ate pretty fantastic. Squid Game showed us Korea has arrived. The empress is very well done (Austrian). French movies are 10/10 for drama. Canada is a mecca for sci fi. Japan's animation is the best in the world. Get out there and see what the world is doing.