New York Times columnist Thomas Friedman said President Trump's election belongs in the same category as other national tragedies such as 9/11 and Pearl Harbor.

In an op-ed published Tuesday night, Friedman said the resignation of national security adviser Mike Flynn offers renewed opportunity to demand answers to the White House's ties to Russia.

"We need to know whom Trump owes and who might own him, and we need to know it now," he wrote. "Save for a few patriotic Republican senators like John McCain and Lindsey Graham, the entire Republican Party is complicit in a shameful act of looking away at Trump's inexplicable behavior toward Russia."

Friedman then likened the election to a foreign attack on the country.

"Ladies and gentlemen, we were attacked on Dec. 7, 1941, we were attacked on Sept. 11, 2001, and we were attacked on Nov. 8, 2016," he said. "That most recent attack didn't involve a horrible loss of lives, but it was devastating in its own way."

Flynn resigned Monday night under intense scrutiny and reports that despite earlier denials, he had spoken with the Russian ambassador about U.S. sanctions placed on the Kremlin by the Obama administration.

The details of the conversations remain unclear, but the White House said Trump requested the resignation because his "trust" with Flynn had been breached.

U.S. intelligence officials have said they believe the Russian government attempted to interfere in the election and swing it in Trump's favor, though there is no evidence that any of those attempts affected the outcome.

Trump, for his part, has repeatedly denied any strong ties to Russia and that he doesn't know Russian President Vladimir Putin.