It looks like you're in the UK, so your araucanas are different from ours here in the US. In the US, araucana is rumpless and tufted. An ameraucana has muffs, a beard, and comes in certain accepted colors. An americana, the way it's spelled in the thread title, is just another name for an easter egger. An easter egger is a mixed breed chicken that usually lays blue or green eggs. It can be a mix of those two breeds, or it might be a mix of another breed that lays blue/green eggs like a crested cream legbar, etc.
In the UK, araucanas are different. They have muffs, they may have tails or be rumpless, and they have crests.
I don't think ameraucanas have made it to the UK from the US.