I know one thing, after being born and raised in Illinois and moving to North Carolina, the difference in race relations I saw down here was astounding. The south has much..much better race relations than the north but guys like Putnam would never study why because they are clueless about the real world.
To the extent this is true [not just different] it is because, happy history or not, the populace shares a history. That makes them more apt to cooperate and to get along with each other. I have also found that southerners are quite willing to accept outsiders once they've shown that they do not intend to remain outsiders.
My favorite part of the article, however, had to do with the attempt at community organization.
A few years ago we held a neighborhood block party, just about every ethnicity in So Cal was involved. City blocked off the street and we had kids drawing chalk pictures and running RC cars all over the place.
Right up until the mexican families (2) who had not taken part despite being invited decided to move the street barriers and drive in and out repeatedly.
Thankfully, they departed fairly soon after and I have a good mexican-American neighbor.
Today the nonparticipants are filipino [second generation in US and by no measure needy].