Out of curiosity, couldn't ASML replace the all of those elements with either their own development or new suppliers?
This is taking into account the worst case scenario, which isn't that unlikely to happen.
I mean, for sure there are these plans in motion already, but how hard would it be?
Not really, some of the IP is core to the product and it cannot function without it. In theory if you do something like come up with a complete replacement for EUV, you could, but everyone with deep pockets has already been trying to do that without success. Same goes for the supply chains, most companies (including ASML) don't manufacture everything themselves; so components that come out of the US would need non-US suppliers, which don't always exist.
I suppose it's a case of 'technically possible, realistically infeasible'.
A more likely scenario might be either a from-scratch not-as-good machine that you can source locally (supply-chain wise) or a novel finding (which is hard to predict if it will happen and if so, when).