Nah, don't bother.
When you arrive, go and buy a cheap Garmin Nuvi from Walmart (or somewhere similar). If you can get a mailing address, buy one off ebay beforehand (
target price about US$70 (£43)) - resell it on eBay when you get back. Ideal for the US tourist.
If you know which model you'll buy, sort your RAM mount and power lead before you go.
Greg