How many Americans are fully aware of the secret wars the US fought in Cambodia and Laos?
I'm confused as to why these educated chinese would know of these things anyway. They're clearly not taught them in China (along with many other things as I have found out as an English teacher here), so I guess you're saying that the education they received in the west should have taught them about them. But does western history education really cover the Sino-Vietnamese war and how many Chinese died in Korea? I certainly don't recall them in my history lessons.
Unfortunately the term "overseas chinese" is such a catch all that it's hard to tell just what sort of peope you're talking about? Students from China or people who've emigrated to the West?
My wife and many of her friends would be considered overseas chinese even through they have been in the UK most of their lives and some are even born there. However, they all are very western and whilst they probably aren't aware of half the events you mentioned because we just weren't taught them in school, they certainly aren't waving the Chinese flag.
On a side note. It's fairly debatable about the Chinese losing the Sino-Vietnam war. Both sides claim victory (as is expected) but it's not like China was kicked back out of Vietnam. Neither did they surrender or sign a ceasefire. In fact on their way out of the country they did a lot of damage to Vietnam.
Admittedly their goal of getting the Vietnamese to withdraw from Cambodia was a failure but does that count as losing the war? Surely if that's the case then America lost it's war in Afghanistan when they failed to find Bin Laden.