Several million people of Vietnamese descent live outside Vietnam. The largest community by far is in the United States, followed by significant populations in Australia, Canada, France, Germany, Japan, South Korea, the Czech Republic, Poland, Taiwan, and elsewhere.
These communities did not all form the same way. French Vietnamese communities have roots reaching back to the colonial period. Communities in the former Eastern Bloc grew largely from student exchanges and labor agreements with North Vietnam. Australian, Canadian, and American communities were shaped heavily by refugee resettlement after 1975. More recent migration includes students, skilled workers, and marriage migration.
Because of these different origins, "the diaspora" is not one political or cultural community. A Vietnamese family in Prague, a Vietnamese family in Paris, and a Vietnamese family in Orange County may share language and food while holding very different histories and views.
What they often do share is the work of maintaining language across generations, building community institutions — temples, churches, schools, associations, businesses — and figuring out how to raise children in one country while carrying another.