Legal Drinking Age?

The United States is one of about only nine or ten countries (Cameroon, Honduras, parts of India, Oman, Pakistan, the United Arab Emirates, the United States, the Northern Mariana Islands, Fiji, and, to some extent, Egypt) in the entire world that prohibit 20-year-olds from buying alcohol. (I exclude from the list countries that ban alcohol entirely.) In what messed-up logic does a drinking age of 21 make sense? Not in any logic I know.

One cannot legally buy (and in many states, even drink) beer, but can wield an M16 in deadly combat with murderous terrorists. Seriously. Does that make sense to you? If it does, there's a petition I'd like you to sign...