There’s no doubt that the United States has made terrible mistakes, like invading Iraq in 2003 and torturing terrorism suspects after Sept. 11. President Barack Obama often drew fire from Republicans for acknowledging the obvious — there are limits to American power and sometimes decisions to employ military force have resulted in “unintended consequences.” American drone strikes against extremists in Afghanistan and Pakistan, for instance, have sometimes killed civilians.

But no American president has done what Mr. Putin has done in silencing nearly all independent media, crushing dissent, snuffing out Russia’s once-incipient democracy, invading Ukraine, interfering in the American election — apparently on Mr. Trump’s behalf — and trying to destabilize Europe. At least in recent decades, American presidents who took military action have been driven by the desire to promote freedom and democracy, sometimes with extraordinary results, as when Germany and Japan evolved after World War II from vanquished enemies into trusted, prosperous allies.

Since taking office, Mr. Trump has shown little support for America’s traditional roles as a champion of universal values like freedom of the press and tolerance. In fact, as he has worked to cut Mr. Putin slack, Mr. Trump has bashed allies and laid the groundwork for an aggressive campaign that could lead to conflict with Iran, which the Pentagon has ranked behind Russia as a threat.

Mr. Trump’s willingness to kowtow to Mr. Putin in the Fox interview was too much even for the Republican Senate majority leader, Mitch McConnell, who rebuked Mr. Trump, called Mr. Putin “a thug” and rejected any equivalence between America and Russia. The House Democratic leader, Nancy Pelosi, urged the F.B.I. to investigate Mr. Trump’s finances and personal ties to find out if the Russian government was blackmailing him.