just a minor note:
During the vietnam war, the drinking age was decided by the states. Many states allowed you to drink at 18--because you could die for your country at 18. This, of course, was the era of the draft.
We have an all-volunteer service (paid, of course) now. If the drinking age is still determined by the states, they have all decided on 21. This has to do with largely physiological/psychological factors. In Sweden, for instance, while you can drink in bars and restaurants at 18, you have to be 20 to take anything home with you.
However, there is an important caveat. If you are in the military, and under 21 (but over 18), you can drink. Granted, you have to buy the alcohol on base (if I understand correctly). So yes, you can die and drink at 18, but you have to be in the military.
When your country no longer tells you that you have to die for it, but asks, it's a little ridiculous to make your statement.