You can easily find it on the Internet, and then remove the word "if".
Not only now, but always VN smaller and weaker than China.
The US will help to build solidarity in ASEAN and to build ASEAN+
You have underestimated the extent of Chinese cunning. They are bad much more than which you can imagine.
Per your suggestion, I read up a little on the killing fields and found that without a doubt Vietnam's invasion of the Cambodia to remove the Khmer Rouge regime and Pol Pot was a great service to humanity, so I edited my post and removed the "if" from there. I could not understand how China could support a regime that killed 2-3 million people, including 200,000 ethnic Chinese, almost 1/2 of ethnic Chinese minority population of around 425,000 in all of Cambodia:
Killing Fields - Wikipedia, the free encyclopedia
So when China decided to punish Vietnam with 1979 China-Vietnam war, it was ironic that China was attacking Vietnam for a great humanitarian act, which saved ethnic Chinese lives in Cambodia. I guess communism in the form it was understood and practiced in both China and Cambodia, did strange things to the leadership and the people that followed them.
Also I am guessing for the Chinese, the Red Khmer (Khmer Rouge) was their "b**tards" and even if they killed a good 20% of their population, they were still ok with it. Killing for the sake of geopolitics and influence or for the sake of an ideology, not good at all, I must say.
This was also probably the Cambodian version of the Great Proletarian Cultural Revolution in China:
Cultural Revolution - Wikipedia, the free encyclopedia
that killed millions (1-20 million, estimate varies wildly it seems) in its own purges and persecutions.
May be you are right about my opinion on the Chinese, because I personally or our people have no direct experience with the Chinese. I do know that Koreans are extremely wary and suspicious of the Chinese, bordering on paranoia. But it may not be that important at this stage of the game. Because the Chinese are still much weaker compared to US/West who still have a combined GDP of 36 trillion dollars whereas China is still at 7.3 trillion (nominal). So the West led by USA still has an economy that is about 5 times bigger than China. Till the Chinese economy reaches close to the Western economy, ASEAN and proposed ASEAN+ would be better off to align with the US/West for the time being.
30 million Overseas Chinese in ASEAN are 5% of the 600 million total population, but probably they are the richest and most economically influential 5% with 1-2 trillion dollars in liquid capital. In ASEAN+ with a billion population, the percentage of overseas Chinese goes down to 3% (30/1000) and the addition of Japan and Korea in this group may cancel or at least balance out a lot of the influence of this influential minority in my opinion, as those two wealthy East Asian countries then may become the most influential groups in the proposed ASEAN+. But it will not be easy as these Overseas Chinese are essentially local people. I think ASEAN in its current form has this critical flaw, too much influence of wealthy Overseas Chinese who control almost all ASEAN countries economy and perhaps politics also and without inclusion of Japan and Korea in the proposed ASEAN+, the ASEAN group may not be able to realize its true potential, as it might be compromised from within. Please correct me if I am wrong about this.
More democratization and public awareness will also help to educate people, so they can make intelligent decisions about their future and thus reduce the influence of media propaganda run by the rich wealthy elite and their pet politicians in ASEAN+ countries. Here US/West can play a good role for strengthening civil society and democratic institutions further in ASEAN+ countries, as well as help with the formation and integration of ASEAN+. But the US/West itself have tremendous problems with their democracy, they have become oligarchies, where the wealthy elite 1% control the media, politics and even judicial system.
But I am not sure how the US feels about ASEAN+. Inclusion of Bangladesh, Sri Lanka and Maldives will raise objection from India, a friendly nation and an US ally, a key player of the new Asian Pivot plan of the US, to contain China. Inclusion of Japan and South Korea may be problematic for the US itself, as these two countries are major non-NATO allies and are integral part of the US sphere of influence. Allowing Japan and South Korea to join ASEAN+ will mean that they will grow their own wings eventually and one day fly away from US sphere of influence as they become busy and involved with their joint "empire" in ASEAN+.