Yes, I was a kid in the 1970s and the anti-littering campaign was pervasive. I was too young to remember/notice the litter itself, but definitely remember the "Crying Indian" commercial, Woodsy Owl[1], and others. You always saw these in the Saturday morning cartoons, in particular.
https://tvtropes.org/pmwiki/pmwiki.php/Main/CryingIndian
>>>> My guess is it will take another generation for people there to appreciate how blessed they are to live in such surroundings but by then it will unfortunately be too late.
This in the parent comment is strange. It wasn't too late everywhere else, and it obviously won't be too late in Vietnam either. A clean environment is a luxury you can afford when you're rich. Poor places are dirty, but it's not like they can't be cleaned.