Back in the 20th century, left and right were convenient descriptions of fundamental political attitudes.
Those who advocate tradition (usually including religious and cultural), authority (a punitive legal system), patriarchy, consolidation of property and wealth, and a defensive, isolationist foreign policy - generally, top-down rule - have been called right-leaning.
Those who advocate a progressive, inclusive, secular, egalitarian form of governance; education, conciliation, preventive law and diplomatic foreign relations - a generally citizen-oriented administration - have been called leftist.
There was no conquering aspect to this division: it’s a perfectly legitimate and honest difference in vision. Most people hold opinions on most subjects that fall roughly within one belief-system or another - but there are always exceptions and dissent; attitudes and situations are changing all the time. Good government is a constant negotiation between the two kinds of approach to whatever issue must be dealt-with, usually ending in compromise.
What’s happened to the US isn’t about left and right. The Republican party has been anything but isolationist or fiscally conservative (No, it doesn’t mean cutting taxes to the rich: it means keeping the wealth of the nation in the nation). It’s made a stand “against big government”, while actually expanding both the powers and budgets of government agencies and the military. They yell about the constitution, but have, in fact, made more changes (not to mention fraud on a grand scale) to election procedure, the franchise, law-enforcement and state power than the so-called left has. The American “right” is no longer conservative - it’s become just a tool of the Koch brothers. They have systematically driven out moderate, informed and reasonable conservatives. That’s how they ended up with the current crop of sorry candidates.
The present divide-and-conquer aspect of American politics dates back (approximately) to Nixon, who blatantly harnessed dormant racial tension to get elected. His right-wing successors have built on that technique, fanning whatever resentments they could, sowing fear, xenophobia and suspicion, scapegoating minorities, gays and women, enlisting Big Pharma, Big Sugar, Big Agro, Big Banks, Big Religion, Big Spies, Big Guns and Very Big Oil, expanding the military-industrial empire, interfering in the politics and suborning the economies of hundreds of sovereign nations, invading dozens … all the while advertising against big government.
The left has all but disappeared since 1965. It’s a poor, ragged rearguard action. Sanders is the last of his kind: a consistent, honest advocate of a liberal, civil society. And he’s old.
You have nothing to worry about: this whole circus is about to fold.
Well, by nothing to worry about, I mean, besides catastrophic weather and civil war.