To answer this, we need to first look at what Robert Putnam says in Bowling Alone. Putnam’s main thesis is that the amount of social capital in the United States is declining. That is, Americans are longer tied together as closely as they once were. There are fewer social bonds between us now than there were in the past. Putnam says that there are four main factors that cause this. First, he says that Americans are generally busier than they were in the past, leaving less time for communal activities. Second, he argues that suburbanization has weakened ties between people because they commute to work in distant places and have less contact with those around them. Third, he says that the prevalence of electronic entertainment (please note that he wrote in 2000, before the era of smart phones and such) kept Americans from interacting in person. Fourth and most importantly, he says that generational change is reducing social capital. This is because the generations that lived through the crises of the Great Depression and WWII are dying out. Their generations felt more ties to one another because they had to help one another get through these terrible times in our history. Later, luckier, generations do not feel such connections.
If these are the main causes of community decline cited by Putnam, we need to think of others that might be involved. Here are a few possible causes:
Greater diversity. In the post-WWII era, people generally lived around people who were very much like them. Today, we have greater levels of diversity than ever before in the United States. We have more racial minorities. We do not share common religious beliefs to the same degree that we once did. These factors make it harder for us to trust one another and to want to spend time with one another.
Greater mobility. I would argue that we are more likely to move around the country today. We are less likely to live in the same town where we grew up, among people that we have known for a long time. This reduces our ability to feel close to those around us.
Political polarization. The American people today do not seem to share common political beliefs. In the post-WWII era, there was less difference between the two parties and more of a common ground. Today, the political parties are very different from one another and people like talk radio hosts on the far left and far right pull Americans farther apart. We are more likely to think that people of the other political party are bad people and we are less likely to want to engage in public activities with people who do not share our political beliefs.
Income inequality. Americans today feel that the middle class is being squeezed and they feel a fair amount of class animosity. There is anger against “The 1 %” who are seen as having a disproportionate amount of wealth and power. There is anger against the poor who are seen as exploiting the government instead of working hard. This sort of anger reduces our trust in our fellow Americans.
All of these are possible reasons for communal decline that Putnam does not emphasize in Bowling Alone.