Our 50 states hang as a single nation. It's like, you know, E Pluribus Unum and all that.
But each has its own governor, courts, legislature and laws. Each can tax and charge its people with crimes.
The original 13 states thought of themselves as being independent. They weren't thrilled about having a national government in Washington telling them what to do. Who can blame 'em?
So they came up with the Tenth Amendment.
It says that all powers not given to the Federal Government belong to the states or the people. Their goal was to keep as much power as possible in local hands.
It's always been tricky.
When the people of California voted to legalize cannabis (weed, dude) for medical use, the Feds said no way. The U.S. denied states the power to set pollution standards and vetoed health plans.
The Federal Government forces states to pay "unfunded mandates" for programs they don't want. It often withholds money to make states to do stuff. And it usually works. Here's one example: the drinking age is the same in most states because they would lose federal dollars by not agreeing to a 21-year age requirement.
Lots of Americans worry that the Feds have grabbed too much power...but hey...as long as they don't try to take over the lotteries.