Great! Accuse a Breton of being a Briton. To make sure he understands, clarify that you’re accusing him of being British, not Britannic, Britonnic or Brythonic. See how it goes down. 
If there were an easy way to distinguish inhabitants of the so-called American continent from those of the USA, something like American vs. Amerigan (or Amerikan?), that would settle this silliness. Unfortunately, we’re stuck with the stupid language called English. If you want Spanish to take over, you know what you have to do. 
In the end though, we are all displaced Pangaeans… 
