Frida Ghitis, a former CNN producer and correspondent, is a world affairs columnist. She is a frequent opinion contributor to CNN, a contributing columnist to the Washington Post and a columnist for World Politics Review. Follow her on Twitter @fridaghitis . The opinions expressed in this commentary are those of the author. Read more opinion on CNN.

(CNN) The images made you catch your breath. Under torrential rains and a canopy of umbrellas , thousands upon thousands of pro-democracy protesters defiantly -- but peacefully -- marched along the streets of Hong Kong on Sunday. China's regime has been trying to intimidate the protesters with credible, ominous threats that they could use brute force to put down the protests. Still, pro-democracy marchers turned out in astonishing numbers for the 11th week in a row.

To the rest of the world, and to many in America, the bravery of the people of Hong Kong comes with a message: Is this what you should be doing?

Organizers claimed 1.7 million marched . Authorities gave a much lower estimate for the initial gathering, but didn't update their figures. In a city of about 7 million, the organizers' estimate would amount to a huge segment of the population. Americans and their friends took notice.

Hong Kong, of course, is not the only place where pro-democracy demonstrators have taken to the streets, recently, challenging regimes with a history of violence, despite what look like dismal odds of success. In Russia, the riot police have been beating and imprisoning protesters who have peacefully demonstrated to call for free and fair elections.

Perhaps nowhere was the courage of everyday citizens more breathtaking and the odds more daunting than in Sudan. There, demonstrators challenged a regime so brutal that its leader, Omar al-Bashir, was charged by the International Criminal Court with genocide and war crimes in 2008. Security forces killed scores during nine months of pro-democracy protests. (A CNN investigation discovered that Bashir's brutal crackdown against peaceful protesters was designed by a Russian firm with ties to the Kremlin.)

Incredibly, protesters managed to topple Bashir. A new transitional government is now in place in Sudan, and Bashir went on trial on Monday. There's reason for some skepticism about whether democracy will follow, but there's no question that without the protests, the dictator Bashir would still rule in Khartoum.

In Hong Kong, protests started as a pushback against a proposed law that would have allowed authorities to extradite people to China for trial. The bill has been withdrawn, but demonstrators have expanded their demands against China's steady erosion of their freedoms. They want more democracy. They are worried about what their future holds under Chinese rule. We still don't know how this will end. After all, the regime responsible for the Tiananmen massacre is massing troops near the border

Hong Kong, Russia and Sudan are only three places where calls for democracy have roiled the status quo, challenging powerful autocrats. But does that mean Americans, concerned about the authoritarian tendencies of a President who behaves dismissively toward democratic institutions, should emulate those tactics?

To be sure, Trump's attacks on the media, his dismissiveness of Russia's interference in US elections, his jokes about staying in power indefinitely, his politicization of the judiciary, his relentless lying, all constitute a threat to democracy.

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But there are enormous differences between what is happening in the United States and in Hong Kong, Russia and elsewhere.

One of the crucial differences is that the United States is still a functioning democracy with a viable path, through existing institutions, to bring about change. If Trump loses reelection, we expect that he will leave office under a system that guarantees that transfer of power.

Mass protests have an important role to play in functioning democracies. That's why it was so significant that on the day after Trump took office, people across the United States staged one of the biggest demonstrations in the country's history, the Women's March. Protests on that scale, or the scale of those in Hong Kong, help no matter what country they're in to galvanize activists and spread their message, energize the population and send a powerful message that the public is paying attention. It is a warning to the government, and a reminder to the population of its own power. The strength is there, coiled, ready to be released with great force if needed.

In Hong Kong, as in Russia and Sudan, the people felt they had no recourse. That's what happens when democratic freedoms vanish.

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For now, concerned Americans can channel their energy into helping turn out the vote, supporting candidates, working for change. Massive marches can help, but real change is still possible through democratic means. If that changes, if Russian interference or voter suppression undercut the legitimacy of the vote, people will think back to Hong Kong's oceans of persistent protesters.