Establish a single age of adulthood (recommend 20).
ALL government policies (federal and state) should then be updated to adhere.
This would include health, licensing, voting, taxing, alcohol, etc.
You are either an adult or an adolescent. There is no situational variance. This policy should provide direction on the expectation for ALL policies to adhere by an “age of adulthood” and that age can/should be defined as XY (e.g.20) if not otherwise agreed by 2/3 of Congress for a different age in an addendum policy.