Nothing particular but after the embargo lift in 1995, the influx of American goods and cultures flooded the country. With the fall of Soviet, Vietnam was on its own for years and the lack of foreign aid dug a rather big hole in the economy, culture and common goods. From then, you have generations of kids watching Tom&Jerry and Starwars instead of Nu, pogodi! and Spadla z oblakov. And American goods are way better than everything available at time from China or Russia so they became more popular. At the time, stuff like milk and canned foods from America dominated the market. Other than that, Vietnam sometimes got economic aids from America and Japan. American volunteers also helped fund bombs and mines removing program in Vietnam, Cambodia and Laos.

For short, America filled the economic and culture holes left by Soviet.