What Does "American Marxism" Mean?

Mark Levin's opening monologue from Life, Liberty and Levin.

""American Marxism," doesn't that sound weird? What does that mean? "American Marxism."  What it means is very simple. These folks like to name themselves: liberals, progressives, social activists, democratic socialists. They are
remember embracing the fundamentals of Marxism, not in every respect, but
in enough respects."