It is true that 'Amercan' English a subset of the English language and therefore not its own linguistic entity. However, in the real world there is enough differences between the two one could consider 'American English' and 'British English' as their own spoken entities despite the fact that they are both English. In this context I don't believe Cgaultokstate is actually intent on saying 'American English' is its own language but it is its own spoken language. Splitting hairs... maybe. Still true however.
Es difícil explicarte la diferencia en breve. Muchas veces, un hablante nativo te entenderán lo que quieres decir si no usas la forma correcta. Hay muchos sitios que pueden ayudarte entender cómo se usan las dos formas del futuro.
Huh, so it is. Apparently you cannot await a person if you are a person yourself. I didn't know that yet.
Still, I'm okay with the translation. :)
Yes, it is incorrect to put the me where you have it.
Object pronouns (like me, te, lo, les, etc,) have some options as to where to be placed in certain sentences. In this sentence, with a conjugated verb and an infinitive, there are two correct options (and Duo should accept both):
Before the conjugated verb: Ellas me van a esperar.
Attached to the end of the infinitive: Ellas van a esperarme.
An object pronoun (like me, se, le, nos, etc.) goes immediately before the conjugated verb.
If the sentence also contains an infinitive, like Duo's sentence here, the pronoun may also go attached to the end of the infinitive: Ellas van a esperarme. Duo should accept (and usually does accept) both ways.