America would be better off with Britain in the EU, as a counterweight to Germany. Britain, however, would be much better off out of the EU, and in an alliance with a Trump-led US. A Brexit vote is therefore a vote on the come for a Trump-led US, because if it passes but Hillary becomes President, the crumbling US/UK relationship will crumble even further—not that this would matter, because the US after Hillary will not be the US.
Oh, do not worry. France will likely follow suit and that will really make the Germans angry as they’ve always thought they should be running France.