> Europe still is in a position, where it feasibly could control 100% of the semiconductor value chain on the continent.

That's not possible. There are just too many different parts going into semiconductor production and they're scattered around the world.

Case in point: the source of the best semiconductor-grade quartz is located in Spruce Pine, North Carolina and while there exist alternatives, for cost-competetiveness you want that.

Hilariously enough it belongs to Sibelco, which is a Belgian company, but it's still US territory, so subject to local politics.

While it may be true that cost advantages are in that specific quartz, it is not some irreplaceable product. It absolutely would be possible to use other quartz, which would require more processing and increase costs.

Do you have any actual examples of things which could not be in sourced into Europe? I am very aware that for many reasons, among them costs, semiconductor fabrication is spread globally. But is there an actual reason why it would be impossible to have every single one of these pieces in some capacity in Europe?

Europe is continually moving further apart politically from both the US and China. Relying on the US for supplies and betting on Chinese, Taiwanese peace seems increasingly foolish. How can Europe secure itself in such an environment, without its own semiconductor supply chain?

Small point worth bringing up, that quartz doesn't go into the ingots that get sliced into wafers (and then doped and diced into chips). It's used to make the crucibles that the ingots are grown in.