Not after the first generation has passed away. There are still some influx of Vietnamese immigrants (people born in and spent a considerable number of years in Vietnam) into the US these days, but it’s not a whole lot. At a certain point, probably another 50–100 years, most ethnic Vietnamese will have been born in the US. How do you keep up the culture of a country you’ve never been to, and have only heard of from your parents?
That being said, I think Chinatown in San Francisco and NYC (for example) still have a healthy amount of Chinese “culture” - still hear a variety of Chinese dialects spoken there. Toisan/Cantonese in SF, not sure about NYC. So we never know; maybe future Vietnamese generations will keep it up, but my expectation is no.
Most Vietnamese born in the US (or anywhere else, really) grow up speaking English, as they should. When I came to the US as a teen, I was quite sad at first when people who carried Vietnamese last names (and sometimes first names) couldn’t communicate well with me in Vietnamese; it didn’t take me long to realize it’s not their fault - in fact, it’s near impossible to preserve what they spoke at home before school age, when school, friends, and the media are all in English. It takes a tremendous amount of effort, practice, patience and love (unless one is linguistically inclined, that’s a different story - most people are not) to learn your parents’ heritage language. So most Vietnamese-Americans aren’t fluent in Vietnamese.
Without a good grasp of the language, most of what they know about Vietnam come from their parents; and there are a lot of changes from the time their parents left Vietnam, to modern day Vietnam in 2020. Someone I know thought that once you step foot in Vietnam, you’ll get kidnapped for a ransom. It pains me but at the same time amuses me that he believes this, because that’s what his dad (who left VN in 1975) taught him lolllll. Even if his Vietnamese is poor (it isn’t great, but passable) and he can’t read well, there are still plenty of English sources out there that give an accurate account of what 21st century Vietnam is like; his thoughts are just so ingrained that he refused to read on his own to find out what it’s really like. My aunt who left the country 20 years ago thought I didn’t know how to use a shower (I was very offended) and was shocked when my English was reasonably good when I came to the US (yes we get taught English, especially in big cities).
Taken those examples into account, I wouldn’t be surprised if some Vietnamese born overseas still think of Vietnam as a mythical war zone. Fortunately with the age of the Internet, most people are pleasantly surprised when they find out it’s, uh, quite different, in a good way ;)
(I don’t want to paint a picture that 21st century VN is perfect - far from it, there are still many things Vietnamese people are dissatisfied with, but at least the problems are workable. It irks me (and honestly it’s very ignorant) when someone speaks “the truth” about Vietnam, only for them to say “Well, I’ve never been, but my parents told me…” It’s like when someone told me he’d never go to Italy because his Italian uncle told him Italy was dirty. When I came to Italy I was like omg that person must never have seen Los Angeles or San Francisco lmao).
It is definitely not what it was like 20 or even 10 years ago. Everyone has their own perception; in order to find out your own truth, you have to see Vietnam for yourself. Otherwise, you can’t claim to know it).