The US is the virtually the only developed country with a drinking age above 18. This is a national embarrassment.
The current drinking age denies legal citizens of a right and discriminates against citizens of a particular age; Citizens who can vote, go to war, sign contracts and are fully responsible for their actions. Further, an 18 year old who is drunk is no less dangerous on the road than a 40 year old who is equally drunk.
This is not and cannot become a medical or safety issue. If the government can deny this right to citizens in a discriminatory manner, they can deny rights to other specific groups, such as senior citizens or religious groups or homosexuals. This is a frightful erosion of freedom for everyone.