Given that Eco describes Ur-Fascism as a *process* (of "coagulation"), perhaps it's more important to describe the nation's direction and whether it's accelerating in that direction or decelerating.
Having read Eco's points and written my commentaries, I believe:
1. The nation has had fascist elements for a long time. This is probably not uncommon.
2. There have been periods when the US was more fascist. (Consider the Jim Crow South 
or the Second Red Scare .)
3. We took a marked turn toward fascism within the last few decades. It's pretty pointless to argue exactly when. The turn of the century is convenient to use as a turning point. Let's say January 17, 2000 .
4. The change has been accelerating for a while and is now (early 2025) moving fascism-ward at breakneck speed.
5. While boundaries are fuzzy, there's a point at which you have to say, "Yeah. Might as well call it fascism." We are at that point.
6. It is "fascism with American characteristics." Nitpicking about whether this or that characteristic is *really* fascist serves only to helps the fascists. The time for that is past.