I think the essential story of the United States of America is a weave of five historical currents:
+ the struggle of native Americans against their genocide;
+ the struggle of African-Americans against their enslavement, and to find their own unrestrained identity;
+ the struggle of immigrants to establish decent lives for themselves and their families;
+ the struggle of labor against its exploitation by capital;
+ the struggle of the Natural World to withstand the assaults by capitalism.
The struggle of women almost everywhere in the world including the United States to overcome the many forms of abuse, depreciation, exploitation and inequality that they can be subjected to could also be added as a sixth historical current of the American story.
All these struggles continue to this day.
I do not think the triumphalist story of capitalism’s ascendancy and of the personal successes of notables gaining wealth and attention, as well as the glorification of American wars and imperialism, is a historical current with any depth of meaning for the definition of “America,” even though it is the predominant ideological myth promoted by the official scribes and propagandists of the American ruling class.
It took me many years to crystalize this realization, which has long been known and expressed by many alert people. So, then I was asked by a friend:
Q: “What happens to societies when people only care about themselves?…”
A: They become very cruel and disunited, and nationalistically weak.
Thucydides describes this as a danger to the Athenian society of his time, during the Peloponnesian War (431-404 BC):
“Some legislators only wish to vengeance against a particular enemy. Others only look out for themselves. They devote very little time on the consideration of any public issue. They think that no harm will come from their neglect. They act as if it is always the business of somebody else to look after this or that. When this selfish notion is entertained by all, the commonwealth slowly begins to decay. ”
It was the leading cause of the Fall of the Western Roman Empire in the middle of the 5th Century, which devolved into feudalism. It is a feature of the moral corruption weakening societies that are subsequently conquered, as was France by Prussia in 1871 (read Guy de Maupassant’s short story “Boule de Suif,” for an evisceration of that class society) and then again by Germany in 1940 (read W. Somerset Maugham’s book “Strictly Personal,” about his travails in France during 1939-1940, and how the French capitalists would have to back postwar socialist policies for the working class, who would do all fighting and dying to liberate France).
Q: “… and unless compelled to act otherwise by some authoritarian or autocratic government.”
A: Revolutions, like the French (1789 and 1871), Russian (1917), Spanish Anarchist (1936), Chinese (1922-1949), Vietnamese (1945), and Cuban (1959), erupt in reaction to endemic societal corruption, cruelty and top-down injustice, and foreign invasion, and they all-too-soon harden from populist-socialism to authoritarian command societies.
While the socialism of the Cuban Revolution is incredibly admirable, and the type of thing needed everywhere (especially in the U.S.A.), it is nevertheless unfortunate that a part of that Cuban socialist solidarity had to be compelled in order to assure the survival of the revolution and the independence of the country from the Colossus of the North. , 
The French Revolution ended with Napoleon (in 1800); the Russian Revolution ended with Stalin (by 1934); the Spanish Anarchist Revolution ended with the Stalinists gaining primary influence over the Republican Government (in May 1937); the Chinese Revolution ended with Mao Zedong; and the Cuban Revolution was spearheaded by Fidel Castro and still struggles to free itself from authoritarian measures imposed because of two political forces:
+ the unrelenting military, economic, diplomatic and propaganda war waged against Cuba by the U.S. (since 1902!!),
+ and by the all-too-human motivation of the Cuban political leadership to stay in control of the Cuban government.
Some kind of force (“Security,” “the Army,” “the Police,” “Intelligence”) is always necessary to defend socialist societies and restrain those who would seek to dominate them, and yet the existence of such forces are themselves breeding grounds for such would-be supervisory dominators.
Q: “I think my question is unanswerable, but I periodically voice it when I feel despair over people’s inability to learn from the past, to go beyond their tribalism, and to fail seeing their intrinsic connections to the rest of humanity. I rail against all that after once again being subjected to other people’s benighted opinions that are examples of those failures.”
A: I see that many people seek to address your basic question with:
+ elaborate political ideologies and theorizing (my Marxist friends);
+ appeals to religious do-gooderism (traditional soft-Christian fluff, largely delusional);
+ commitments to charitable social work in hopes that that ethic spreads by their example (real do-gooderism with hopes for the future, perhaps in vain; as done by exceedingly admirable people like Dorothy Day);
+ progressive political activism, (mucking in the tedious turgid nitty-gritty of party politics, like Alexandria Ocasio-Cortez and Bernie Sanders, extremely admirable people trying to be pragmatic in advancing progressive policies — or as some would say “lesser evils” — that seem to have some finite chance of reaching fruition; such efforts are derided by Marxist and Anarchist theorists, who consider them ideologically ‘imperfect’ and incrementalist: pipe dreams);
+ all out revolutionary action in hopes of sparking a general uprising (being a violent outlaw like Fidel Castro at the Moncada Barracks in 1953 and in the Sierra Maestra in 1956-1958; a delusional and destructive alternative most of the time, but on rare occasions it works);
+ giving up and sinking into hedonistic dissipation or self-terminating depression (a very sad and yet too popular option, which in the extreme can lead some to emulate the Marquis de Sade or become suicide bombers).
The options and resources available for solving a difficult problem depend very intimately and strongly on the attitude you bring to the situation confronting you, and the attitude you are prepared to live with in order to obtain a solution. This is very clearly seen when contemplating the problem of the sustainability crisis characterized by global warming climate change and biodiversity loss, faced by our fractious capitalist world.
My own rather Fabian-Utopian approach (in answer to the question) is to urge action in response to global warming climate change, because I know that to really solve that problem (the sustainability crisis) will require:
+ social unity (the problem is planetary, there are no local nor piecemeal solutions);
+ a leveling of standards-of-living (worldwide!);
+ massive demilitarization (resources reallocated for broad social benefit);
+ a heavy reliance on intelligent planning and Earth-focused scientific research and engineering (technology for human and social benefit, including those for nutrition, drugs and medical care worldwide);
+ and de-growth de-capitalization (economics as if people mattered
+ a.k.a. socialism
+ and resource reallocation and employment for broad social benefit).
The compulsion for advancing such global initiatives would come from Nature itself in the form of the rapid erosion of the sustainability and climatic conditions of the many environments provided by Planet Earth to its human tenants. In this analogy, Nature becomes the autocrat dictating our conformity into World Socialism. I suppose this is a grimly utopian view.
Nature’s sustainability-crisis push on our bitterly fractious self-focused human world society seems quite capable of producing the same kind of effect on us as the German invasions of Rome during the 4th and 5th Centuries had on the bitterly fractious self-focused society of the Western Roman Empire: the collapse of a rotten structure into impoverished chaos out of which violent strongmen would carve out fiefdoms in a new Dark Age, and perhaps this time the last one.
On the other hand, maybe Nature’s sustainability-crisis push will spark a world revolution in human thinking and humanistic identification, and from that a totally new world socialist paradigm will come to define organized human life on Planet Earth. It is all a matter of choice. Only time will tell.
Thanks to Ann Harmless for prodding my thinking with her questions.
 Cuba and the Cameraman
 Cuba Libre