Your questions have little to do with anarchism. You are describing situations where people do not want to do anarchy (as in collectively sharing ressources for the improvement of living of all people, practicing solidarity and prioritizing cooperation over domination). Anarchist are not forcing people to to anarchy when most of them do not want to do that).
And I think " Don’t just tell me, show me on a map how it will work." this is just a bad faith thing to do when you are not willing to make a similar effort. Your examples are of literally two communities when on a global scale there would be uncountable communties. Please make your examples more realistic, so options such as intercommunity solidarity, reasonable alternatives for food sources and isolation of colonialist communities are actually available options.
And if you really want detailed anarchists programs on how to distribute resources, this section of the anarchist FAQ highlights some theoretical attempts at that with citations so you can actually dive deeper into this. Many of the cited texts should be freely available.