Contrary to my fellows, I basically agree with your main point -- though I also agree with the counter that Eco's definition of fascism would consider America fascist -- but ultimately when I said that his definition was inadequate because it doesn't touch on the basic mechanics of fascism at all, your solution was to mystify by saying "well, they're diverse".

Here's the problem with that: You're still identifying all those states as fascist despite the preponderance of diversity that is such a concern for you. This leaves two possibilities:

Fascism is basically a rhetorical style, not a genuine political ideology
There is something in the mechanics of these political movements that allows you to call all of them fascist

I think that 1 is the much flimsier point. I'm surprised no one has given you a good account of 2, but the really short answer is that it is what happens when capitalism as a mode of production comes under threat (especially from itself) and capitalists unite to find a way to clear-cut more room to expand in, while defending capitalism and its instrument, the state, with the greatest viciousness from any challengers either one face. It is capitalism panicking.