American talk in the middleof ..

I have heard that Americans talk in the back of the mouth. Is that right?

I've never heard this and I have no idea what it would be referring to... We have front vowels and in some dialects there is vowel fronting... We don't have many consonants that occur behind the velum... If you mean we sound like we have a sock in our mouth or something, I guess... I've heard that English sounds like a lot of vowels to someone who's never heard it because of all our diphthongization... Is that what you mean?

We talk in the front of the mouth, and sometimes in the middle of the mouth. I don't recall ever talking in the back of the mouth, before.