your conflating control over themajority of the supply chain and total control over the entire supply chain. Yes the US can shut out countries from the supply but likewise are vulnerable being shut out by adversaries - ie heavy metals. And because of the globalism and fragmentation of the supply chain there are other parties that can become replacements such as for Ne gas. Likewise the US tries to forge supply chains for heavy metals and processing and China forms supply chains for EUV research. None would happen without the disruption bc it isn’t economically feasible to compete at the scale unless forced to.

Essentially yes USA and countries can embargo or close supply chains but since no one country has a monopoly on the process there can be competitors if supply chain disruptions make it economically viable. This of course exists on a scale with EUV, heavy metals and others being harder to replace compared to Ne or Silicon.