It will absolutely take years (or the better part of a year, if all parties involved are willing to go WWII-level readiness about it, which they likely wouldn't be). But
when would you rather be doing that: during a cool economic standoff, or after a hot war starts?
The United States is vast, and the North America continent even larger. I doubt there's any element or mineral that's not viably extractable somewhere in North America. The extraction cost might not be
competitive, but that's a different issue. The American "Deep State" has known this was coming, and has not been idle. (Although Trump is quite capable of deliberately or inadvertently sabotaging such plans in countless ways - one of many reasons why America's adversaries will celebrate his return to power.)
For example:
US Critical Materials makes gallium discovery at Sheep Creek in Montana (March, 2024)
Two Australian companies are pursuing federal funding to jump-start antimony mining near Fairbanks and Anchorage. (November, 2024)
Germanium is a bit of an odd duck compared to the other two (or to other rare earth elements). It's common, but not typically concentrated. The US has the world's only germanium mine (which also produced gallium), in Utah, but it's been closed for years. Global germanium production recently has largely been from reprocessing the ash from burned coal (typically using ash from power plants, as it is easy to get in bulk), although it's also possible to extract it from minerals with some germanium content, typically zinc ores.
This cut-off is only likely to accelerate existing American and others efforts to find alternatives. With regards to the US and China, it's a trigger the CCP should only get to pull once, and using it for this actually seems rather foolish (unless they're planning to invade Taiwan Real Soon, at which point this is pretty much the ideal time to use it). On the other hand, the US (especially under Trump) is quite possibly dumb enough to leave themselves exposed, to be hit by this tactic repeatedly over the next decade or two.