This is a common misconception about the US. Here [1] is a graph of foreign born population in the US. It previously peaked at around 14.8% in the late 19th century. This started causing substantial anti-immigrant sentiment to emerge as it was felt to be having an overall negative affect on culture, society, labor, etc. That eventually led to various restrictions on immigration sending it to a valley of 4.7% in 1970.

That graph is by decade; the actual valley was probably more around 1965 because That's when a new immigration act was passed that greatly loosened the requirements and immigration rates began skyrocketing to where they are today at around 14.8%, with rising anti-immigrant sentiment emerging for the same reasons, at almost exactly the same percent. Note that 14.8% includes all groups, including illegal aliens. The number of foreign born residents in Japan is, and has been, much lower.

[1] - https://www.census.gov/library/stories/2026/07/foreign-born-...