The chip foundries used are NOT in China! China has zero cutting/bleeding edge foundries and it will be many years before the lithography technology needed for 10nm and lower nodes is sold there.
TSMC is In Taiwan and of course Samsung is in Korea. Yes Intel has foundries that could be used but their best tech is reserved for their own usage. Sidebar to that, Intel has always used a different definition for what a node-size is: Intel refers to the metal layers vs the gate size. Technically, Intel's 10nm node is equivalent to about TSMC/Samsung 7nm nodes.
Back to foundries in the US, Global Foundries operates a 7 & 5nm foundry in upstate New York.
Interesting! Tangentially, what do you make of this?
https://www.zdnet.com/article/korean-researchers-develop-ternary-semiconductor-tech/https://bizwhiznetwork.com/samsung-backed-researchers-debut-ternary-semiconductor-design/Samsung put a ton of money into this group. Interest in ternary seems to be making a resurgence, and I'm keeping an eye on any developments. I think we're still some time away from production at scale, but this could be a major shift in ASIC mining? Ternary seems to have been collecting dust since the late 80s.