Can Congress p this and Obama make it mandatory?

The Age of Majority meaning you are an adult.in three states its not 18 but I think in everystate it should be 21 again since society doesn't see you as an adult till you are 21 anyway.They have 18 plus and 21 plus there needs to be ONE only.raise the age to fight in war to 21 if they need troops draft people again make it 21 and over.Most people 18-20 are in college they have too many age restrictions,in other countries things are one age only.Can the government repeal the 10th amendment and make a national age of majority since society doesn't see it different ages.lowering it was a big mistake in the very first place.in Alabama its 19,Nebraska 19 and in Mississippi 21.Mississppi is the only state that has it right.