Anything. EEs aren't a real breed, they're just a mix that usually lays green or blue eggs. The question is, what do you hope to accomplish with the cross? Then we can tell you what you might want to make a cross with. Also, the real breed is spelled "Ameraucana". "Americana" is just a term hatcheries came up with to label their EEs. If the person who sold you your bird called it an "Americana" then what you have is already an EE.
