Actually the Ams and Araucana's were both developed from the easter egger! Blue egg laying chickens were brought to the US from south america and from there we they were separated and bred for certain traits, like rumpless/tuffed, or beard/muffs, egg color, feather color. So all the people who say your EE is a mixed breed Am are incorrect. Your Am is actually a standardized EE. Sure, the hatcheries have taken it and run with it(like all breeds. Shoot, look at their RIR. and thats where you get the EE's today) but which came first, the chicken or the egg? The ameraucana didn't just, poof, appear here. However. To keep the breed true you should only cross Am. to Am. Adding in any EE, even if you cross back to the Am for many generations, will still be an EE. It'd be really hard to get that standard back. When people have a breed they want to improve on they usually take the breed and start crossing in another breed that has the traits they want. Then over the next x amount of crossings they try and work out the unwanted traits they've brought in. Thats how people get new colors in a breed. By crossing to another, but you have to bre careful, because with an AmxEE you are basically "breeding down". I learned always breed up and try to improve. With any type of animal.
Now let me just say I'm an EE owner. EE's and Olive eggers. Have not owned an ameraucanas yet. I'm actually picking up a blue Am this weekend though. (along with 2 more EE's!)