To be honest, every foundry is in easy reach of something that can take it out. If there's a conflict that results in missiles hitting Korean factories, someone will be drone-bombing the power interconnects or driving trucks into water purifiers or whatever and taking out foundries in Texas.
It doesn't take much to ruin semiconductor foundry throughput. Wafers spend weeks or even months progressing from stage to stage. If you can cause a power failure, for example, you can scrap the whole content of the line and there will be no output until the pipeline refills: https://www.forbes.com/sites/tomcoughlin/2019/07/05/nand-fab...
Perhaps process robustness is better now, but in the constant scrambling state of semiconductor manufacturing, I doubt it is better enough to be able to shrug off concerted, deliberate attacks rather than just accidents, fuckups and bad luck.