Probably less than the number of young Chinese men of military age that are in the US right now on educational and H1B visas. Think outside the box. It's better to have lots and lots of people already inside, with lots of cached weapons and demolition gear, than to try a conventional move against the US military.
How would the US street gangs react to suddenly being provided with access to heavy-duty weaponry? How would the US economy do if a couple hundred sniper teams with .50 cal tracer/incindiary rounds started taking out gasoline trucks on US highways at rush hour?
Now THAT is more than plausible!
And along the lines that I've pondered for years.
I've often wondered how loyal the 'students' et al would be who are already so well placed within our society.
I think that's a hazardous thing for China. I think many would not be loyal to China. And, sadly, many we think might be loyal to us, would not be.
But yeah, they have thousands here and plenty would be loyal to China to cause us great grief, imho.
And, Mexicans for Aztlan (not called that then) had plenty of cached weapons hidden in the Southwest at least as early as 1965. I talked with such critters in my job at the univ library.
The interesting tangential evidence of this is that every few years, US Customs finds a COSCO container full of military weaponry (labeled as something else, of course) while spot-checking imports. And every time, the Chinese government says they'll investigate the matter and you never hear about it again. This has been going on for years. Since they only catch them in random checks which only look at 1-2% of the containers overall, it does make you wonder how many containers full of weaponry make it through to have the occasional one randomly caught.
And I still find the fierce nationalism of Chinese here, including some that were even born here, to be a bit odd. Most other Asian cultures have gotten past the overt master race complex a long time ago, even if the subtext is still there. In most countries it is now muted to the level of how Americans generally think we're better than everyone else -- a matter of pride and history rather than the axiomatic Word of God. A lot of Chinese believe it is the destiny of their race to rule the world or some such, which is slightly disconcerting vocal assertion coming from born and bred Americans. (Can you imagine the press coverage if white people openly said such things?)