Since the night of November 8th 2016 the whole Western world, United States included, has been asking the same question: How could Americans elect President Donald Trump eight years after choosing Barack Obama?

In the course of months of analysis many factors have been mentioned, starting with the fears and frustrations of that part of the white electorate whose votes gave the NY real estate mogul his razor-thin victory.

These factors, whether economic, social or political, have undoubtedly contributed to Trump’s unexpected win. But none of them goes to the sociocultural root of the matter.

To my eyes as a European-born American, Trump's election is the most recent - and acute - manifestation of a trend that in the last few decades has been making American society and democracy more similar to their European counterparts.

I call it “the verticalization of America,” and I refer to a process that in the course of time has been modifying a country born out of the “horizontalist revolution” that so inspired Alexis de Tocqueville.

The famous 19th century French political scientist was most impressed by the horizontal nature of a decentralized society that educated its citizens to political coexistence as well as being involved in public life, a powerful push that counterbalanced the other competing cultural force, that of individualism and the Darwinist self-sufficient spirit of the pioneer.

For another century and a half, “horizontalism” provided stability to American democracy. Because of that, when the 1930’s depression pushed many Europeans towards what we now call “nativism,” Americans were able to withstand the nationalist sirens by choosing the enlightened road of the New Deal.

In his many works, Harvard political scientist Robert Putnam attributed the robustness of American society to the abundance of its "social capital." In his book, Bowling Alone he described two forms of such capital, “bonding” and “bridging”. The first form strengthens the bonds (and the power) of its members. The second one builds consensus among groups representing diverse interests. The first is vertical, the second horizontal.

Ever since the Middle Ages with its arts and crafts guilds, in Europe (and in my native Italy in particular) the vertical form of social capital has been the dominant one.

In the United States, on the other hand, since the days of de Tocqueville the horizontal form has been much more prevalent. At last it was until recently.

In his last two books, Putnam has been issuing ever more alarming warnings about the decline of that bridging spirit that for over two centuries produced social capital in massive doses.

Throughout its history, the United States has had a number of socio-economic equalizers, which fueled the lore of the American Dream. First there was the westward expansion, then the New Deal, and finally the great industrial growth of the postwar period.

But starting at the end of the 1970s, that cycle of equalization came to a sudden stop. This produced a gap of both income and opportunities that lead to a growing “verticalization” of society.

Socio-economically, the richest and the super-richest moved way ahead of the rest of the population.

Politically, an electorate that for decades swung between two contiguous parties, started to become much rigidly divided, with the urban centers increasingly turning into “blue” islands in the red sea of rural America.

This division was reinforced and crystallized even further by the continuous redrawing of electoral district boundaries by the party in power, AKA as gerrymandering.

In terms of public participation in the political process, intensely bonding forms of associations, such as the Tea Party or the ever-growing Super-Pacs, overcame more bridging forms, such as the traditional think tanks and even the much less divisive old versions of the Democratic and Republican parties.

This verticalization process has not spared the media.

When I moved to this country, in the late 70s, I was impressed by the fact that the only significant division in US journalism was horizontal, the one that separated news from opinions, while in Europe the division was mostly vertical, between the political left and right.

In 1980, when Ted Turner launched his all-news cable channel, that horizontal division was still intact. Like the network evening news, CNN had intellectual honesty as its guiding principle and objectivity as its goal.

Thirty seven years later, that principle and goal are largely ignored by the two dominant news channels of today, proudly positioned on the right (Fox News) and the left (Msnbc).

Trump's victory has been the most striking expression of a trend that is transforming America into a society that isn’t interested in building bridges anymore. In fact, a significant part of the country seems intent in taking down the existing ones.

My hope as someone who wasn’t born but chose to become American, is that the "horizontal" antibodies that historically protected the oldest and deepest democracy in the world will manage to find ways to bounce back stronger than ever.

Otherwise it would be the end of the only form of American exceptionalism that deservedly won the unanimous admiration of the rest of the Western world.