I don’t think a video can convey how difficult: I think a video could make a run seem easier than it is, equally could make it seem more difficult. And it is certainly normal for a run to be rated based on its most difficult/challenging section, however short.
Otherwise, gradings can vary from country to country: I’ve never been to America, but I have been told by a couple of people who have skied in USA that the gradings there are higher than typical in the Alps (i.e. a typical red in the Alps would be graded black in USA).
True, but that’s for the simple reason that the US doesn’t have such a thing as a red run! Instead, you have single black diamond or double black diamond: single is basically a European red, double is a European black.
Once you make that very minor mental adjustment, US and European classifications are basically the same.
