If it is called Americauna, then it is really just an EE. The real name is AmerAUcana. Hatcheries mislead people all the time by using a similar name - Americana, Americauna and sometimes the real name, Ameraucana - for EEs. Most people don't know any better and fall for it, unfortunately.
I don't know about Meyers. They're probably mixed, but I can't say for sure. I've never had them.
A lot of hatcheries do NOT misspell Ameraucana and therefor neither do the feed store that sell them because they don't know the difference. Misleading, yes. Illegal, no. :/ They are like the blind leading the blind in most cases.
That being said... EE are great. Will always have a couple in my flock.
And even when you buy from breeder doesn't guarantee quality... I ended up with leakage on my Black/Blue Am, and bent toes on my Salmon Faverolle, as well as my OE still laying the nice dark Marans eggs (but has sprigs and doesn't lay olive)... but one of the pure Marans doesn't lay dark enough eggs. Even show lines will not produce all show quality chicks, ever IMO. It's still a matter of selecting the best of the best from that batch.