How popular is Vietnamese food in foreign countries ?  

I feel like it isn't quite as popular as kpop is, not yet at least. It is getting there though and I am sure it will grow in the coming years.

I think it depends. I have seen some restaurants in my area but they are quite small. No chains or anything. It seems like it is the kind of food that is still spreading. I think the UK only just started getting more "American" style restaurants so I guess it takes time. 

Vietnamese food is pretty darn popular in foreign countries, but it really depends where you live.

In the U.S., you'll find that it's most popular on the West Coast, and especially in California, because so many Vietnamese people moved there after the end of the Vietnam War. In cities like San Francisco and LA, there are entire neighborhoods where it seems like every other restaurant is a Vietnamese joint!

The same is true of several European cities, too. London, Paris and Berlin have especially large Vietnamese populations—and lots of restaurants—because some Vietnamese people were able to escape to those areas during the war. And now their children and grandchildren are growing up at home with traditional foods, getting to know their grandparents' recipes and culture.

It's also quite popular around places where a lot of foreigners visit or live, such as Korea, Thailand (lots of tourists) and Japan (lots of business professionals).

There are areas where it is but I find that none of them compare to actually eating the food in Vietnam. I think most people would agree with that.