Vietnam doesn't have the population to be the next China. I wish them the best, but their time will not last nearly as long as China. (or more likely it lasts as long but it is shared with a bunch of other countries in Asia, Africa, and/or South America)

Nowadays, with so much automation going around, Vietnam can afford to become the next China even without a comparable population. Not that I think it will, but see the story of the Four Asian Tigers to realize how smaller countries can suddenly have a much bigger importance to the world economy.

Made Americans a lot richer and allowed them to consume more?

Made the Chinese even more richer and technologically superior to the us in many many areas as well.

Yes, it's a win-win situation.