There was a unified Korea, led by Lyuh Woon-hyung.
Americans arrived afterwards, Lieutenant General John Hodge said: "one of our missions was to break down this Communist government".
If the Americans wouldn't have come, there wouldn't have been any north/south division (in fact, Kim Il-sung wouldn't probably end up leading a country). And you somehow think that it's China who destabilized it?
Similarly, it's the US that invaded Vietnam from the other side of the world. The only difference is that the country was already divided, after the Anti-French Resistance War. You think of it as "communist aggression", but the truth is that these were liberation wars from western colonization.
Similarly, the US propaganda personally blames Mao for "killing" people due to a famine. The reality is more complex, and unfortunately personal responsibility of state leaders is never recognized during these events. Similarly, Trump is "killing" hundred of thousands of people due to his mishandling of the pandemic, but we both know that he won't be held personally responsible.
I can get into more details, but you should reconsider what you choose to spread. If you're just repeating propaganda talking points, you're not going to accomplish anything good for the people in Korea, Vietnam, China or US people themselves. The only people that you're doing a favor to are the fat cats in Washington.
China didn't displace tens of millions of people in the middle east from their homes, the US did.
China didn't destabilize dozen of countries (via assassinations, coups, and other unsavory ways to initiate regime change), the US did.
There's one threat to world peace, and that's the US. It's ridiculous that people think that somehow China could be worse than that.