It is not so much about English and Americans, but about learning a first language as a child versus learning a second language later in life. Learning a second language usually involves learning the grammar, and explicitly learning the rules that native speakers "just know".

I think it is quite plausible that, for any language, speakers that learned it as a second language will know the grammar and grammatical terms better than most native speakers (particularly monoglot ones).

Since you provided many examples, I will also give a few:

An astounding number of people overcorrect to "It was a present for my wife and I" or so, having trouble with the few remnants of cases (nominative, accusative, genitive) English still has. Similarly, many native speaker seem incapable to identify the much maligned "passive voice". Or, ask a native speaker under what circumstances you'd use the past perfect continuous.