There was a great Economist article a while ago that talks about this. ASMLs moat isn't just the know-how to build the machines themselves. It's a network of suppliers all across Europe, specialized businesses doing one little part better than anyone else in the world.
This is the type of thing that Europe is still leading in, and it'll be incredibly hard to reproduce elsewhere.
You don't just need to figure out how to build an High-NA EUV machine. You need to figure out how to build or procure all of the parts that go into it. Many of these suppliers have exclusive contracts with ASML.
Here's the article, de-paywalled: https://archive.ph/jP1HX
Of course, producing the EUV beam in the first place has also not been duplicated and it's Californian technology.
Intel 18A has a different strategy all together. I mean, it's not like they're saying much about it, but from the little we know, it's very different.
Free electron lasers are not hard at "mere EUV", and the accelerators to feed aren't either, it's just that an efficient setup requires recycling the beam which means bending it back which means a large (factory hall sized) accelerator at the beam energies needed for good EUV light.