The possible "taint” that could embarrass the US is defeat in the hands of their opponent and they will also have a taint if Vietnam becomes a communist country.
The Definition of taint is one that connote a contamination of any kind. It can be morally, corruption wise, defect etc.
One thing the United State is afraid to is to Fall into the hands of their enemies. This will bring their power down and also affect their economy greatly.
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