The Legal age for drinking in The U.S.A. is 21 and by then your not a teen anymore.
A little lesson in federalism... The US federal government does not setup what the drinking age is. As with most other crimes, it is up to the states to decide what is considered a crime and what the punishments should be when the crime is committed. For example, murder is usually considered a state offense, not a federal offense. In the case of the drinking age, the federal government tries to persuade the state governments to establish the 21 drinking age by withholding federal transportation dollars if they make the drinking age less than 21.
This is why several of the posts say stuff like "Teens can drink as long as they're with their parents"; again that is what is allowed in that particular state, but not all states have that law. In Utah up until last July, it was illegal to drink alcohol in any public establishment regardless of age -- you could only drink in private clubs (which meant that
bars "private clubs" would charge a
cover-charge "membership dues" to be able to go into them). This is also why Wisconsin was discussing dropping the drinking age to 18 in the state. Their reasoning was that the tax revenue generated by the lower drinking age would offset any moneys lost from the federal government.
As for my feeling about what the drinking age should be... I believe that there should be an age of maturity set where all "adult" activities are legal: drinking, voting, signing-up for the military, watching *bleep*, smoking, etc. Now whether that age should be 18 or 21 I feel is open; it just does not seem right that a person can vote, fight in a war, etc. but not be allowed to drink. I actually think that 18 would be a good age. This is the time when most people are moving out on there own, either by going to college, going into the military, or even just working on there own. Most will have graduated high-school by then and are making plans for their adult lives.
I also think that the "age of majority" idea should encompass some things that are much younger in other states (and may be upsetting to many out there). If there was to be an age of majority, I think that driving, getting married, and having consensual sex should also fall under that purview. For a lot of these other things, teens are also too immature to handle correctly. People complain about the number of accidents teens would have if the drinking age was lowered, but teens are already having a high number of accidents because of their reckless behavior behind the wheel (which is why insurance premiums are so high for young drivers).