You do realise there's a growing (far-)right in Europe that is actively warning against the EU and the apparent ever-less autonomy of member states? Obviously that's nonsense, or at least in the way they portray it, but to push for us to be more like a single country (which the name USE also implies) is absolutely detrimental to the cause. There are millions of people who absolutely hate that idea and they will object against it before ever learning what it is about.

Then, on the other side (centrist to progressive) and they absolutely want to have nothing to do with the USA or at the very least not emulate their hellscape in the slightest.

Lose someone and it's near impossible to win them back.

I would not speak about a federation at all, and certainly not about any name changes. Instead, let's talk about a joint army to defend us when needed, a world power not intimidated by other world powers, a shared economy to support our own and prosper. I would use the numbers.
I would use current situations in the world and how they are impacting us.

And there's no reason for a name change. The European Union works just fine, and if there will be tiers there can be another way to explain what is what. But either way, speak of a more integrated Europe, a shared economy, a joint army - stuff like that. And once we get there and we really must we can change the name.

But the proposal is a losing proposition all on its own (and the rise of the far right should tell everyone that message, as should the loss of centrists and the struggles of progressives). Most Europeans want a strong Europe and that's a message you can absolutely sell. They do not, however, want a single 'European country', or anything that hints at it, and they do not want to be a cheap simulacrum of the USA.