Why are there hundreds of thousands of Miao people in America?

There are many Miao people in America, but not absolutely. They are Vietnamese immigrants. During the Vietnam War, due to Vietnam's ethnic minority policy (the main ethnic group in Vietnam is the Li nationality and the Miao nationality is a minority), ethnic minorities were persecuted and basically "defected to the angry sea". Some of them went to Hong Kong, Malaysia and other places, and most of them took refuge in the United States.