The Commerce Clause gives Congress the power: "To regulate Commerce with foreign Nations, and among the several States, and with the Indian Tribes." This has been widely construed as meaning that states cannot make taxes that affect other states' citizens unless they are doing business in that state.
The Supreme Court has just ruled that their earlier ruling (that Store A had to have some physical presence in State S in order for S to require A to charge sales tax) is wrong, and no such physical presence is required.
Did you pay income tax in the state, which will be what supports the university? Congrats, you get in-state tuition.
>>Drive a car into my state? You have to pay a roads tax.
Two points: 1) you are using the roads in the state, why can't you fund them? 2) that tax already exists, you pay it when you buy gas.
Most things are pretty similar state-by-state, but it can be really nice being able to pick your laws if you have to. Maybe you love weed and you want to pick a state with legal weed. Or maybe you like drones and want to pick a state with fewer drone laws. So many things differ state-to-state, from REAL ID to trans rights to surveillance to taxes to guns to driving age to social aid to public transit. Gay marriage, slavery, and interracial marriage were all issues of the past but they were very important in their day too.
I do think it's an important part of what makes America America, and being able to "pick your laws" is an amazing freedom that most people don't have.
Now, the actual ability to move wherever you want can sometimes be limited. If you're in Vermont and you want New Hampshire laws, well, that's easy. (Differences: weed, guns, advertising, taxes, many more.) But if you're in Maine and you want Hawaii laws, a move like that probably isn't doable. Still, I think it's a valuable freedom.
We might actually see some movement in this direction now.