I can't speak for other Americans (USA, in particular, which is who I assume you meant), but for me it's the nature of the oligarchical regime and their views on individualism. I've read the Chinese CSL, and spent a couple of days in a session presented by international lawyers and security professionals explaining what it meant for our business, how we needed to navigate it, and how it was being implemented. It's scary.

Information is power; specific information about you is power over you. It's control.

As for the government, I think it's more a matter of the fact that China is far more well positioned and equipped to surveil US assets. Russia is bumbling, pre-occupied, and doesn't make any computer components we use. Chinese chips, on the other hand, are in everything. The US is worried that, in a conflict, we could discover that China is able to simply... turn off all of the F35s. Or shut down or coopt firing systems on our war ships. Or disable coms or NV gear of ground troops. All of our modern equipment is computerized to more or lesser degree, and the failure of even seemingly simple resisters, sourced from China, could result in misoperation of gear, at best. If the espionage is more sophisticated, with more important components, it's conceivable China could locate and monitor assets; missiles which ignore counter measures and always hit because the target is broadcasting a homing signal.

Most off these hypotheticals are probably not within the realm of current technology, and that what access China is able to embed in computer components is far more limited. But we don't really know, and it's far more dangerous to underestimate than to overestimate capabilities.