Drinking is a very common thing across the United States of America. The Federal drinking age was 18 years old, but with the National Minimum Drinking Age Act of 1984 it changed it to 21. Individual states can change it to lower, but this would result in a reduction of 8% of the states annual federal highway apportionment (money given to the state for highways.). And for most people this makes total sense, do not let kids buy alcohol because the will abuse it... but ironically enough its the opposite. 

The reason I say this is because when you make something sound bad and not let a kid do it, they are going to try to do that thing and in this case it is drinking. Don't get me wrong there are still tons of drinking problems in Europe , but kids learn how to drink alcohol from their parents. I personally know someone who lived in Germany until he was an adult, and he once told me how the drinking age for him was 16, and this makes sense because it gives people the option to learn how to drink with their parents around versus in their apartment when they are 21 and drinking to much then doing something stupid like driving. But if the U.S. allows parents to have a glass of wine with their children at dinner this would have kids know what alcohol is like and not want to go out drinking with their friends as much, because it is not a foreign thing to them.