This seems a wild generalization to make, though I guess "be suspicious of newcomers" is a little biologically hardwired. What's your epistemology for believing "newcomers" are "the ones to avoid"?
This reads like that pattern where people assign blame for all issues to whatever thing they happen to not like. The US is the least individualistic it has ever been, but there was much more community and less loneliness in the past. That make it pretty obvious that the issue here isn't "individualism".
You are saying that in the past, more resources were spent supporting individuals than the resources spent supporting communities and yet communities were stronger. That sure would be an interesting thing to understand if true. My interest is certainly piqued, seems too good to be true though.
Our lopsided emphasis on individualism, our definition of economic efficiency that does not include the mental health value, these have been detrimental to our connections, roots, community, family etc.
We said, let the mom and pop stores die, their replacements provide the same value but more efficiently. Let community bonds die they intrude upon our individual destiny.
But we did not correctly account for the value provided by those that we chose to replace. So it is not surprising that we find ourselves here.
Could it have played out any other way ? I doubt it. Our world is an underdamped system, so we will keep swinging towards the extremes, till we figure out how to get a critically damped system. The other serious problem is that the feedback system is so laggy, that's a biggy in feedback control loops.