Yeah, you've basically got it. China announced these new export restrictions on certain materials vital for tech, batteries, etc. New rules mean US companies need permits and have to meet certain conditions to import them. So Trump's threat is a reaction to that; it's a back-and-forth thing.
The problem is tariffs don't just affect China; they increase expenses for US manufacturers who need those materials, which leads to higher costs and market instability. That's probably what's affecting your investments. It's a standoff where both sides are trying to get an advantage, causing uncertainty for everyone.