He's painting all the members of a group with the same brush. The fact that this thread is entirely focused on relationships, the "Woman" component to American Woman, is the focal subject, not the American part.

Also, given that he lives in America, i'm guessing that the majority of his experience (although yes, this is a leap to conclusions) is with American Women, hence, he's still making the same incorrect inductive leap from his sample. America is a big place, and i'm guessing he's not really familiar with American Women in their totality.

Hence, misogyny: he's judging the entire group (negatively), based on his limited experience. Particularly, since this judgement comes w/o any actual analysis of his negative experiences upon which his claims may or may not be founded.