Who benefited from the Vietnam war

Communists

Explanation:

Communists in Vietnam, and possibly the USSR for nothing but bragging rights...Really an unfortunate and pointless war for most everyone involved in it. On a financial level many U.S. corporations made huge profits, such as the producers of chemicals like Agent Orange (Dow Chemical, Monsanto, etc.), weapons manufacturers, rubber companies, etc.

In reality hardly no one did.

In a socio-political view, America took a huge leap forward in political activism and social reorganization which might have been many years away but for the war.

But I can say the Soviet Union gained valuable data on the employment of their equipment, at little cost to themselves. They produced and sold large volumes of military hardware. Communism was spread to another country. They got to watch and laugh as their opponent ground itself bloody trying to win a tricky war that it wasn’t prepared for.

to act quickly in times of danger to the united states

because you have to act quickly if you want to live/survive.