For an American of a certain age, that realization is perhaps the most distressing take away from American electoral politics since the turn of the century. Once the realization sinks in, the immediate response is, 'hey, what happened?' Fortunately for most Americans, the realization hasn't sunk in yet. Unfortunately, it's only a matter of time before it does. And, when it does, the country will require luck of heroic magnitude for that to happen without excruciating political trauma, social upheaval, economic suffering and physical violence.
Look at the basics. Politically. Two of the last three presidents (Bush and Trump) have been inaugurated after losing the popular election. Both of them have been the preferred candidate of the 'one percent.' In the last four congressional elections, the party (the Democrats) that has won millions more votes that its opponent has been in the minority, and that opponent (the Republicans) has controlled the national legislature. Again, the Republicans are the party of the oligarchy. Whatever you want to call these outcomes, don't call the result a representative democracy governed by its elected political leaders. Economically. Look at the skewing of incomes and wealth in favor the extremely wealthy (quantifiable), the destruction of unionized labor (historical fact) and the erosion of the economic security of the middle classes (real and perceived). To put it gently, a rising tide (if it's even still rising) is no longer lifting all the boats. Socially. I won't dwell on that one, because Americans get all itchy and uncomfortable thinking about social class (the fact that dare not speak its name, rather like homosexuality in Oscar Wilde's day), but by virtually all measures, social mobility in the United States has collapsed, and, compared to other advanced countries, American society is stratified to an extent comparable to Britain at the height of the Empire (without the safety valve of emigration to the White Dominions).
What does this mean? It means that a politics premised on cooperation, migration towards the middle, moderation, compromise and shared, mutually agreed goals, is a politics based on hypocrisy or a misunderstanding of the realities of the situation. It means a politics that will be successfully manipulated and controlled by subsets within the culture that have a better understanding of those realities and exploit them for their benefits or agendas. It means that the tools of consensus building, expertise based policies for technically complex issues, and assumptions about the ultimate good will and reasonableness of one's political adversaries will be abused, dulled and eventually discarded.
In short, it means we are not all in this together anymore.
Note--a man named William Kitteridge wrote short stories collected in a book titled We Are Not in This Together, published back in the 1980s. Cumulatively, the stories are bleak, austere and depressing. I think he was ahead of his time.