Dont know about the customs regulations, but I wouldnt buy a laptop abroad just because of the lack of after-care. I'd want to know that there was a person on the end of the phone in this country, and (ideally) an address I can drop it off at.
A colleague bought a bargain laptop abroad but it packed up just out of warranty and even though it looked like a standard Compaq, the parts were different to the ones supplied to the UK, and repairing it would have cost more than a new one. And even if its under warranty you will probably end up having to pay to post it to the US, and it will be gone for a long time!