Jeb Bush in an interview with Breitbart made it clear that the US political establishment would of course do a trade deal with a UK outside the EU:

“Great Britain is a sovereign nation, and they must make this decision about their relationship with Europe on their own. The U.S. should not be putting a thumb on the scale and certainly shouldn’t bully an ally. That said, as President, if Great Britain made that decision of course the U.S. would work with them on a trade agreement.”

It really is inconceivable that the biggest economy in the world would not want tariff free trade with the fifth biggest economy in the world…