Don't think anyone really knows yet

by CJM , Friday, June 24, 2016, 19:37 (3080 days ago) @ ~JM~

It will be interesting to see how many free-trade treaties Britain manages to sign before it formally leaves the E.U. trade umbrella. The vote has been taken, but it doesn't specify a particular date that Britain leaves the E.U. News articles are talking about two years before Britain actually leaves the E.U.; but a lot of negotiations have to happen first.
The more free-trade treaties Britain manages to get signed and in effect to replace the existing E.U. free-trade treaties around the world before actually leaving the E.U. the less the economic disruption the Brexit will cause. And most of the economic pain will be felt by Britain if they don't get free-trade treaties signed, I don't think the U.S. will be affected very much as long as whoever replaces Obama is willing to get a treaty done.
As far as international diplomacy, Britain will still be a part of NATO, and still be a special friend of the U.S. Our relations with the E.U. could actually change for the better with Britain not part of the E.U. "inside" discussions and being seen as that special friend of the U.S. from the other E.U. countries. The eastern European states and Baltic states are still going to want the U.S. to protect them from Russia and will be pushing the rest of the E.U. to allow that; and will probably push all that much harder without a vote from Britain being available.