I have heard this claim before, but I haven't been able to find any strong evidence of this. Can you provide some links to places this has happened to? Developed countries specifically.
For example, small UK villages presently having emotion-filled community meetings unable to cope with the negative effect of sudden influxes of 1000's of allotted refugees radically changing every aspect of their home.
But why require evidence, when the basic math has it:
You have x number of people with y number of resources. What will happen if you increase x without also increasing y?
> You have x number of people with y number of resources. What will happen if you increase x without also increasing y?
Places with lots of people tend to be richer. Compare eg New York to Appalachia.
See https://en.wikipedia.org/wiki/Economies_of_agglomeration