There’s also the fact that a hypothetical end to US aid wouldn’t end EU aid. It’s definitely not on the same scale as the US due to our much smaller military sector, but that’d likely change in the event of a US shut-down of aid.
In my mind, the most likely results would be:
Short-term: Very dangerous period for Ukraine, they lose some ground, lots of men (similar to the last time they had a crippling artillery shell shortage).
Medium-term: EU military sector slowly ramps up to meet demand, as about 3/4 of central & eastern EU considers this an existential war that cannot be lost at any cost.
Long-term: After the war is over (however many more years that takes), Russia finally negotiates some kind of ceasefire where they can save some face internally and brag about how they “Denazified” Ukraine while going home and accomplishing nothing, EU is much more self-sufficient and therefore buys less from the US, and they aren’t seen as a trust-worthy ally militarily anymore. Even if on paper most EU members are still in NATO, they consider the security guarantees of the EU as much more important and serious.