MOSCOW -- It's the latest sign of the diplomatic breakdown between Russia and the West. Russian diplomats who were expelled from the U.S. arrived back in Moscow on Sunday. In the propaganda war, one image President Vladimir Putin didn't want the world to see was the return of Russian diplomats and families from the U.S. -- and they went to great lengths to avoid it.

They're ramping up the rhetoric too: Sunday afternoon Foreign Ministry Spokeswoman Maria Zakharova went so far as to suggest the U.S. and Britain are conspiring to take this year's soccer World Cup championships away from Russia.

The worsening crisis between Russia and the West has already seen a wave of tit-for-tat expulsions.

They are triggered after Britain and its allies sought to punish the Kremlin after determining it was "highly likely," Moscow was behind the chemical agent attack of Russian double agent Sergei Skripal and his daughter Yulia in Salisbury, England four weeks ago.

But it's the U.S. reaction that matters most. And Valerii Garbuzov, director of the U.S. and Canada Institute, told CBS News it's President Trump's unpredictability that makes the current situation so volatile.

"[Mr. Trump] is a man with a chaotic mind who can do one thing today, the opposite tomorrow, and the same thing the day after," Garbuzov said. "In words he congratulates Putin on his presidency, in deeds he expels diplomats."

As they lowered the American flag at the shuttered U.S. consulate in St. Petersburg, there's no telling when it will fly again.

Commentators both in Russia and America agree on one thing: the crisis has the potential to plunge toward a deep freeze worse than the Cold War. Back then, there were back channels specifically designed to avoid confrontation. As the U.N. secretary general António Guterres put it: Those mechanisms have been dismantled.