I don't know where you've gotten your ideas that China was insulated against the external world or that's even what the protests were about. The protests happened in 1989. By that time Mao had been dead for 13 years, diplomatic ties to the west had long since been established, and emigration was at an all time high. The first KFC was opened in China in 1987, two years before the protests. China by 1989 had achieved a massive amount of success in their education reforms and were nearing full literacy. Tens of thousands of exit student visas were issued per year. Please don't characterize Chinese people as confused or unaware of outside countries. They have a robust education system and have access to foreign media and literature. I mean half of China right now is addicted to South Korean TV dramas.

The protestors were there for various reasons, and I believe initially many were protesting against the impacts of the 1983 economic reforms, which...were liberalization reforms to ease restrictions on things like international business and travel. Many of those Tiananmen square demonstrators were pro-Mao if you want to wrap your head around that. You can find multiple images of demonstrators displaying images of Mao prominently if you go looking for them. I should also mention many of the issues the protestors raised were addressed with the 1992 economic reforms, which was an attempt to overhaul the economic stagnation China had during the 1980s.

And I did give you two examples of the US military being used against American civilians. Kent State and the 1967 Detroit riots. Both instances had soldiers firing automatic rounds into crowds.

I'm assuming I'm talking with you in good faith, by the way. I hope you'll read some of the other comments in this thread because they're a lot smarter and well informed than I am.