The smaller "Chinatowns" in the U.S. mostly died out due to a combination of:
1. Extreme racism of the late 19th/early 20th century, when armed mobs literally chased them out of smaller towns and cities (this same dynamic happened throughout the rural north with black people - in the Reconstruction era, the rural north was fairly integrated, but this fell apart within a few decades).
2. Even when the U.S. was accepting a lot of Chinese immigrants in the 19th century, they accepted something like ten men for every one woman. Given the great taboos against marrying white women at the time - and the low status of Chinese immigrants - most of them died old and childless.
There are some rare examples of places where there were substantial numbers of American immigrants. Liberia is well known of course, but
there's a peninsula in the Dominican Republic where many people are descended from American Freedmen. There's also
Americana in Brazil, which was founded by white Confederates after the Civil War.