I don't think that this is necessarily the case. Of course there is a gradient. Scopatz can probably draw up a nifty three dimensional graph which shows the relationship between clannishness, family, and competition, but I'm talking about the trend I see in everyday America. I consider myself pro-family. I love families, and the virtues of great parenting cannot be expounded upon enough. In terms of competition, I'm so so. I believe that competition has its place. I'm a free marketer, but I don't expect the market to solve all of humanity's problems, and I definitely don't expect it to solve them humanely, but as a guiding principle, and all else being equal, I think competition is a good foundation for economic relations, and mediocre foundation for political and social relations, and like almost everything, self-destructive in the extreme.
But if you take the "my family's wants are more important than anything else in the world," and add it to, "anything I can get is mine because I can get it," the sum is clannishness. You show that bias for your family and competition against everyone else, it can and does manifest in atrocious practices.
I don't think the problem lies on the pro-family side, though the Saudi/Russian Government with political positions and academic degrees being handed out based on geneology is a little extreme, dangerous and irresponsible.
It's the competition side. When everyone becomes either on your side and an enemy desperate to destroy you, therein lies a problem. There is a passage in Aristotle's "Ethics," I think, where he says that one would not want to commit theft or murder, not for fear of being caught, but because the criminal will see their crime in everyone they meet,i.e., the world becomes peopled with potential theives and murderers.