US is the best CV nation. Why?
Because the differences between the CV's (Nation wise) are mainly about planespace. Sure, there are other differences, but this is the one that matters.
Any nation with more planespace can only put on a few extra fighters. That advantage is negated because US for some crazy reason has the best fighters by a long way, and are the go to CV for competitive play.
It doesn't matter if a CV has better bombers or scouts that US (apart from T5 scouts); Because fighters kill them anyway.