I also think that controlled immigration can work well in terms of integration — if you take a few people and introduce them, and they assimilate, then there is not that much resentment among the majority. But large numbers can cause resentment
I agree with both your posts: that the phenomenon operates regardless of the ethnicities in competition, and that it can be reduced by deliberation regarding immigration *and* I would add, by limited government and by efficiency.
Competition in a free (or free-ish) labor market is one thing. Competition for government “benefits” is another: anything “given” by government to one group must first be confiscated, by the threat of force, from others.
At this point Afro-Caribbean culture has well integrated into English urban culture and has been for many generations.