I don't know about that guys. When I was in Vietnam there were lots of armored vehicles all over the place. Keep in mind that Vietnam is not all jungle. So I think there are actually two questions here.
!. Were there many fighting vehicles used by the U.S. in Vietnam?
Ans.: You bet. We had all kinds. Tanks:M48 Pattons, we supplied M41s to RVN units, M551 Shermans, M88, M578, and M51 Recovery Vehicles, and M278 CEVs come to mind. There may be a few more that I've left out.
2. Was armor useless in Vietnam?
Ans.: A big NO. Armor played a big role in VN. Have you ever seen the film of North Vietnam's final assault on Saigon? Yep, they rode their tanks into the city.
I was in the Central Highlands of Vietnam. You might think that because it was a mountainous and densely vegetated area that armor might not do well. Read this and let me know what you think
http://www.rjsmith.com/ben-het.html