Why didn't american troops invade north vietnam?

The American troops did not invade North Vietnam because of multiple reasons, some of which were the strong support from the allies, relatively large military, and the geography of the terrain. North Vietnam was heavily supported by the Soviet Union, so they had weapons in abundance. Also, the military was relatively large, and it was very familiar with the battlefield, while the Americans were not able to wage war properly in Vietnam. The biggest problem with the geography of Vietnam was that it has lot of hills, highlands, lowlands, all covered with dense tropical rainforest, were there was lot of rainfall, animals that are dangerous, and diseases. The Vietnamese did not had problems with any of those as they were used to it, so they had a huge advantage.

payments were made after the 1940s.

in the 1980s, a commission held investigations and made recommendations.