Culture evolves, but slowly and on a trajectory.[1] Immigration changes the trajectory in a very visible way. You can compare places in the U.S. that experienced more versus less immigration. For example, the taboos against showing off your wealth are still strong in Oregon where my wife is from.

[1] The French refer to "les payes Anglo-Saxon," the Anglo-Saxon countries: https://www.jstor.org/stable/24517581. The term describes the deep cultural and political commonalities between the UK, Australia, Canada, the U.S. and New Zealand. Before the mass immigration of the 2000s, Toronto and Sydney were more similar to each other than I think residents of either city would want to admit.

Would also this means that all sorts of interference with other countries is also bad and should not happen? I can think of a couple of countries right now with a massive problem of illegal immigrants on ships but they use uniforms