Rice
It was never popular; it was unknown.
Chess
Tea.
Dot Kich (Cross Fire) & Audition Vietnam
noodles i think
Noodles are popular because that was the only food they could have
The U.S. feared that Vietnam would vote for a communist government.
This depends on your purpose of tourism. North Vietnam is the most popular of the two destinations.
There are very many popular dishes in Vietnam but I think this website will answer your question better than I can, the pictures showing the dishes are beautiful. http://vietnam.sawadee.com/food.htm
It was an issue which divided the US.
Nguyen