The United States needs to pick one age for adulthood and legal rights
So in the United States the supposed age of adulthood is 18. However there are many contexts where a person can‘t legally have certain legal rights and abilities until later or even are granted before turning 18 (You can drop out of school in most states as well as get a drivers’ license in most states at age 16 as well as be tried in adult court well before 18 in most states but can’t legally drink alcohol or gamble in a casino until turning 21). But honestly the U.S should really just have one legal age of adulthood and not multiple depending on the specific context.