Driving through, compliance in one's home state is respected by the others.

If you move to another state, though, you must comply with your new home's regulation. A car doesn't keep its initial reg plate/number here as they do in the UK. If you move, it gets a new number plate in the new state of residence. If you sell your car even within the state, it will get a new reg plate (with a few exceptions like antique/classic plates can be transferred in Pennsylvania).