If you rent a car, your UK license is perfectly good, and if you book from the UK, all the typical optional insurance coverage is included. (Way better price.)
I drove my father's car in the US with no issues. I carried my UK license along with the counterpart before they did away with that, and afterward with the DMV generated code that you would typically show when you rent a car. My father's insurance covered 'any licensed driver', so I was fine to drive.
Again, you can just let your license expire, but depending on your state, it's better to generate a paper trail to prove that you no longer have ties. Virginia has even been known to use a library card to insist you have ties; most states are not as ridiculous. It took us over a year and a mound of paper to get a ruling from the Tax Commissioner in VA that we had changed domicile, and in my case, I had only been in VA for 11 years out of my then 65. Again, it depends on the state; as I recall, seven states try to hold onto you forever and expect to see that tax return forever more unless you make a formal petition for change of domicile.