The world is frighteningly locked in a battle to the death between democracy and authoritarianism. On Sunday Vladimir Putin issued a new threat to the west – telling his defense minister and his top military commander to place Russia’s nuclear forces on alert.

It is a new cold war.

The biggest difference between the old cold war and the new one is that authoritarian neo-fascism is no longer just an external threat to America and Europe. A version of it is also growing inside western Europe and the US.

It has even taken over one of America’s major political parties.

The Trump-led Republican party does not openly support Putin, but the Republican party’s animus toward democracy is expressed in ways familiar to Putin and other autocrats.

Trump Republicans continue to refuse to acknowledge the outcome of the 2020 election, claiming without evidence that it was “stolen” from Trump. In many states, on the basis of this big lie, they are making it more difficult for people who don’t share their beliefs to vote.

In several states they are laying the groundwork for ignoring the popular vote altogether and throwing a future presidential election to Trump or another strongman. They have stopped even pretending to be the party of free speech: they are banning books from schools and prohibiting teachers from talking about America’s struggles against racism and homophobia.

Putin’s attack on Ukraine, starting 24 February, and the attack by followers of Donald Trump on the United States Capitol on 6 January 2021 are different, of course, but they resemble one another in their contempt for democratic institutions and their attempts to justify violence by asserting a threat to a dominant racial or ethnic group.

Each also represents the logical culmination of leadership by a dangerous narcissist who flagrantly lies about his intentions and his opponents and who sees the world only in terms of his personal power.

Donald Trump has long admired Vladimir Putin who, evidence shows, personally authorized a secret spy agency operation to support a “mentally unstable” Trump in the 2016 US presidential election. Believing that a Trump White House would help secure Moscow’s strategic objectives, Russia’s spy agencies were ordered to use “all possible force” to ensure Trump’s victory.

Again in the 2020 election, according to a recently unclassified report by the US office of the Director of National Intelligence, Putin authorized “influence operations” aimed at “supporting Trump” and “denigrating President Biden’s candidacy”.

Presumably Putin supported Trump in 2016 and in 2020 in part because of Trump’s disdain for Nato. As president, Trump did all he could to undermine the organization, even suggesting the US should withdraw from it. Is it pure coincidence that once Trump was out of office and Nato remained intact, Putin attacked Ukraine?

Defending democracy and standing up against authoritarian neo-fascism requires courage. In 2019, the Ukrainian president, Volodymyr Zelenskiy, refused Trump’s demand for help in rigging the 2020 election in the United States, even after Trump threatened to withhold money Congress had appropriated to help Ukraine resist Russian expansion.

Today, Zelenskiy won’t be bullied by Putin. He turned down America’s offer to evacuate him, saying: “I need ammunition, not a ride.”

Zelenskiy’s courage in the face of overwhelming brute force has fortified Ukrainians now defending their country against invaders.

Contrast this with the toadies at the Republican National Committee who in February censured Republican representatives Liz Cheney of Wyoming and Adam Kinzinger of Illinois for participating in Congress’s select committee investigating the events of 6 January, and who called the attack on the Capitol “legitimate political discourse”.

Also contrast Zelenskiy’s courage with most elected Republicans who still refuse to stand up to Trump. On Sunday, on national television, Senator Tom Cotton refused four times to condemn Trump for calling Putin “smart” and “savvy” and Nato and the US “dumb”.

Make no mistake: Putin’s authoritarian neo-fascism has rooted itself in America.

It may be possible to prevent Putin’s aggression from spreading to the rest of Europe. But it is not possible to win a cold civil war inside America without destroying the United States – another of Putin’s objectives when he ordered his spy agencies to help Trump.

In the months and years ahead, those of us in the west who believe in democracy, the rule of law, human rights and truth, must do everything we can to win back our fellow countrymen to these same overriding values.

• Robert Reich, a former US secretary of labor, is professor of public policy at the University of California at Berkeley and the author of Saving Capitalism: For the Many, Not the Few and The Common Good. His new book, The System: Who Rigged It, How We Fix It, is out now. He is a Guardian US columnist. His newsletter is at robertreich.substack.com