Earlier quoted context omitted.
>>> walk into a random local government office and hand them That is exactly how it works. You go to the customs and hand them bunch of filled papers to proceed with customs clearance procedure. Also you cannot simply import a car to USA, unless it is for a "demo" purposes or 25+ y.o.
So where exactly? At the border? Someplace else? If you were having a car shipped (literally) to you from overseas then presumably customs clearance is at the port. What if someone buys a 1 year old car (any Brand, not just BYD) from Canada - what import fees would apply?
What fees to pay depends on the vehicle. Could be a chicken tax there as well
Also you simply cannot import for personal use a car which was not certified to be sold in USA.