A fairly significant percentage of our Soleheaven.com sales go to the US, and various other places too.
We charge ex-VAT, and send using Fed-ex.
If the items are of reasonable value, the customer may be charged a levy by US tax authorities on entrance to the country. It is worth mentioning this in your terms and conditions. It will be on a relatively random basis, it seems, but regular. And, of course, is completely within their rights.