Being too advanced is not about the raw capabilities of an aircraft. Yes Viggen does pack more of a punch than most aircaft in game (don't just compare it to Phantoms), but that's really not the factor here.
It's a complex plane to model FM wise and from a technical standpoint, with many other unique features to take into account, it is more advanced. It has elements we don't yet have in game in any capacity.
I have no idea where this raw weponary argument came from. But please do not attach that to me.
As for the US, they get more aircaft because they have