One of my former students was asking about Emerson and Nietzsche. Quine even. Here was my first reply:
Nietzsche was vocal about his admiration of Emerson, especially in his The Gay Science. One of Emerson's essays mentions the over-soul.
A lot of Emerson's impact has been dampened by those who think "American philosophy" is insignificant. Nietzsche was didn't bother with such a view. In at least one instance Nietzsche wished he thought in French or English, Walter Kaufmann, if I remember correctly also claimed Nietzsche was aware of American English