Response was: Yes, Italy could choose to do so. However, American would probably delete Italy if Italy made that choice.
So France would not be looking at the US deleting Italy for no reason.
I think we're have strayed too far from the point of ´might makes right' is bad, actually. GP very clearly chose Italy as an example because it's less polemic than the obvious option with a enormous manufacturing base and nukes.
You really think the French are going to sacrifice themselves to avenge the Italians?
To be clear, if we are talking about a salt-the-earth level conventional bombing for pure annexation / genocide of a EU nation the French would:
1. Remind the US via diplomatic means that they have nuclear subs and the will to use them.
2. If ignored, select some non-mainland territory (PR or Hawaii) and make a ultimatum. Mention that if the US does not desist they will wipe it, but will not launch attacks on the continental US.
3. Repeat 2 until they stop or escalate.
The French would absolutely do this, the thing you propose is so beyond the pale (even now) that the only conclusion is that the French would be next.