If NVIDIA can't sell GPUs to China, will that marginalise chinese technology? Or will it help supercharge a local industry? It might do both - hobbling chinese AI in the short term, but helping chinese competitors emerge in the medium to long term. US tariffs are the same. They might "marginalise" the US economy. But maybe they'll revitalise the US manufacturing industry too? We'll see!
The EU has a tremendous number of smart software engineers. They're more than capable of recreating the US technology stack locally. Especially with the benefit of hindsight, and with access to opensource software. In the long run, I wouldn't be surprised if Europe ended up richer by building their own tech stack "in house" instead of outsourcing to US hyperscalers.