An alternative manufacturer, but not a supplier, no.
The US exerts sufficient control over ASML that this will not happen without NATO ending. And the end of NATO (which would be a geopolitical shift more profound than the Fall of the Berlin Wall) and a replacement with some Chinese EUV light source risks the scuttling of all ASML facilities and devices. This is vapor above a coffee cup.
The scenario I'm imagining is in fact the US further destabilizing NATO, in which case Europe wouldn't feel bound by any of the agreements we've made with Americans. Failing that, I don't think any of what was said above is relevant.
The US exerts sufficient control over ASML that this will not happen without NATO ending. And the end of NATO (which would be a geopolitical shift more profound than the Fall of the Berlin Wall) and a replacement with some Chinese EUV light source risks the scuttling of all ASML facilities and devices. This is vapor above a coffee cup.