It’s a Friday night. I’m at a cafe with two high-school friends, savoring a glass of beer. I’m 16 years old. And what I’m doing is legal.

If you haven’t figured it out already, I don’t live in the U.S. I live in Belgium. As in much of continental Europe, it’s legal here to drink beer and wine from the age of 16, and spirits from 18. My American friends tell me how they can’t sip a beer in public until they’re 21.

For...