"so far (after many years of travelling to the US) I am unaware of any tourist tax rebate scheme for the US."
A few years ago I recall leaving New Orleans (Louisianna) and claiming the sales tax on clothing I had purchased on the way out of the State to New York (ie I wasn't even leaving the country, immediately). Not sure if the refund scheme is still available.
Yeah, the sales taxes in the US are all state taxes, and hence all with different rates and rules regarding refunds when leaving the state, shipping to people in a different state, getting stuff from another state shipped to you, etc... complete nightmare.