He was commenting specifically on American culture when he wrote this. I understand him to be talking about looking at life as a “zero sum” game, thinking that we’re in competition for the good things in life, so that one gains only at the expense of others.
That kind of thinking comes from our acquisitive spirit: happiness comes from getting this or that. We don’t know what “this or that” may be (because nothing acquired really satisfies for long), but we know we don’t want others to get it instead of us. This is in contrast to a culture of everyone seeking the common good.