Guys, I think you missed a very important detail....
The Germans (and their Gerry cans) occupied France. The French occupied Indochina. The french had all those Gerry cans the Germans left when they were chased out. The French took them to Indochina with them. The VietMinh chased out the French...leaving behind Gerry's cans. The Americans then came to Vietnam......
It's the six-degrees of separation theory.