Without Song Hong (red River) river, you think your Nord Vietnam will survive?
. You Viet are totally at the mercy of China, if we start the water war, 1/3 of Vietnamese (33 millions) will have to learn to drink sea water, we can easily destroy your farming and agriculture economy and the domino impact will result a total chaos to Vietnam.
And before you talk about exchange water for safe passage in Striate of Malacca, China can make you a counter offer: try to set blockade on Malacca not only you doom yourself to access this passage but lost all the reefs and Islands in SCS...that is your bet.
What a sub-Mekong fantasy dream
, Mekong will never exist without Chinese's water
regardless if US sanction or not.