Americans don't understand their system, but it's pretty clear that they do question it given the political tension, and increasing amounts of riots that we currently see in US. These are the direct result of people being discontent with the direction their lives are taking under the US capitalist system. No amount of propaganda can trick people into thinking the system works for them when they see their lives suck.

On the other hand, vast majority of people in China support their government because they've seen their lives improve dramatically with each and every decade. That's the tangible material difference between the two systems.