It should be up to each state.
If you're old enough to buy cigarettes, go to war, and gamble (among other things), then you should definitely be able to drink alcohol at 18.
The laws here regarding drinking don't affect me personally but they are strict. I do believe the age should be lowered but because more problems will inevitably stem from a lowered drinking age, I tend to be more indifferent towards the whole ordeal. What I wish we had was a much more laid-back attitude towards drinking and alcohol in general, like the Europeans have. Unfortunately that's never going to happen and I'll forever have to listen to friends who think the time the Mexican waiter in Cancun offered to put a little vodka in their drink was such a cool and bad-ass moment.