I am well aware of them. Canada works in the same way as the USA, except that the sex law is the federal government's power (because it's a criminal law). But Canadian federal government has less power than the US federal government. The Swiss government is even more "weaker" than the Canadian and US counterparts, yet it has the power to set an age of consent. If Switzerland and Canada, all federations, could do it, I cannot see why the USA shouldn't. And I don't see why it'll shatter the centuries-old traditions of having the state powers if the US federal government sets an age of consent.
I have to add it wouldn't be the first time that the USA does this. For example, it wasn't the federal power to decide on the drinking age, but the government managed to "blackmail" the states to either raise the age to 21 or the states will not get highway fundings. The government forced the states to accept "Leave No Child Behind" law by threatening to pull out education money if the states do not comply, despite the fact that education is solely state power. The federal government pulled this stunt many times.
Frankly I don't give a shit. Who really does? Stories of teenager sex in national parks speak themselves enough. I'm just surprised there are really some people who take this seriously and they all tend to be gay.