You absolutely should remember the Chinese war with the first of those; if you have trouble, a good way to remind yourself is that it was not long after the US one.

Tibet, Manchuria, it should be somewhat obvious that a nation that is as ethnically diverse as China was not a nation borne out of lots of different people deciding simultaneously that they would like to create a country together.

What is modern China has only existed for 100 years or so. When the country collapsed there were ethnic divisions that were erased after the country was unified.

The hallmark of successful ethnic cleansing is people claiming that there were never any wars, that things were always this way. The same is true of Kaliningrad, the most German city, centuries of history as a leading nation within Germany and the HRE, now a completely Russian city. It is only in the West that you see any narrative around division, in places like China or Russia history is erased (and how could it be any other way, the cornerstone of Chinese politics is one nation, one people...there is no political value in this narrative in Western countries).

It certainly wasn't a denial. China could learn a lot from that.

Since the late 60s there has been explicit federal legislation. I assume you meant this as a rhetorical question but there is a definite answer because the US is a transparent system. Law is passed, the courts enforce.

The fact that you are unable to answer this question about China where it is often unclear why certain people are being targeted should demonstrate how big the gap is. For example, when Xi's first corruption crackdown happened, it turned out that it was being orchestrated in part by someone in their 90s who had left front-line politics twenty years ago (and much of why that happened is unclear, we are only just learning about things that happened in Chinese politics multiple decades ago so it will be a while before we know...we do know that Xi was then able to make unilateral sweeping changes to his own role shortly after that broke every convention of the last 5 decades)...it is difficult to compare this to anything that happens in any other political system. In China, you find out someone has been executed for reasons that are obviously not explicit months after it has happened.

It is genuinely quite difficult to compare to anything else. 6 people meet in a room, they have almost all the power, and maybe you will read about what they might have said 4 decades later in a book...that will never be published in China.

The inability to conceive of a country where these things would happen and you would have no idea that it had ever happened...and, perhaps more importantly, wouldn't care that you didn't know.

I think you're kind of missing the important bit; there is no threat of invasion and there never has been. People just want reasons to be mad at Trump, and so they make things up