Which sanctions?

China is prevented from buying advanced EUV lithography, advanced Nvidia chips and as of monday RAM memories made with American tech.

And what's preventing China from building their own EUV lithography? They can do whatever they want internally regardless of US sanctions. It seems like they're not trying very hard, or are wasting resources on unproductive initiatives.

There's only a single company ASML that does, so this is a global technological challenge.

Not sure what are you trying to get to.

Of course they are also investing in their lithography equipment, but still, it's an insanely complex set of tools and know-how required that's backed by countless patents and well kept secrets.

Without being glib... It is hard. And they will be able to do so relatively soon because though it is hard there is now an immense need to do so.

Only because China is threatening to take over the country producing those chips and seizing territory in the South China Sea in violation of international law.

If China played nice with America.. there's no problem.