Additionally, Chancellor Merkel has also taken a hard-line against giving the UK trade benefits without also maintaining EU immigration rights. President Obama has said that Britain will have to wait in line to negotiate any trade deal with the United States.

It's likely much of the rhetoric is just politicking. The EU and the United States both need the UK as an important trade and political partner. The EU in particular can little afford to see already sluggish growth stagnate further.

The Republican-controlled Congress has been supportive of the Brexit vote, and a bill is already before the senate to push for faster trade negotiations. For her part, May's speech was primarily meant for her party's consumption at the convention, in contrast to her prior remarks which indicate a more collaborative exit.