What happened in the U.S. has made European democracies more resistant to propaganda, Russian or otherwise, and more savvy about cybersecurity. On a higher level, Trump's victory has forced these nations to look at themselves in the mirror -- and populist parties have dropped in the polls from Brest to Dresden.

If Putin gets credit for helping to elect Trump, he should get some for Europe's rejection of populism, too. European democracy is stronger today thanks to his trolling of the U.S. in 2016.

Is the U.S. stronger, though? During his Senate hearing, former FBI Director James Comey warned that the Russians "will be back." What will the U.S. see if Putin tries the mirror trick again in a few years?

They will probably still see a bitterly divided country, but perhaps one that's more serious about its electoral choices, one less inclined to treat politics as winner-take-all sporting event -- an approach that yielded a frustrating, flawed choice in 2016. Next time around, voters will see honesty and decency as crucial assets, and perhaps the major parties will respond to this by selecting contenders who embody them more than Trump and Clinton did. Perhaps these contenders will also be savvier when it comes to cybersecurity and, in general, modern communication. The global technology superpower needs leaders who are better, not worse, at technology than the average American.

Perhaps there will also be a more open public debate -- still contentious and aggressive, but, this time, informed by a better understanding of propaganda mechanisms and the way information spreads across social networks. The U.S. public may get smarter about how it processes information: It's getting more media literacy training than ever before.

Perhaps I'm overoptimistic and the U.S. won't learn anything from this experience except that Russians are evil. But I have faith in the U.S.: Even when I traveled the country during the 2016 election campaign, I felt its vibrant strength behind all the frustration and confusion. I rather think the lessons forced on the country by that campaign will sink in.

No one will thank Putin the troll for that, and he doesn't want America's thanks. If the U.S. public gets smarter about its political choices, Putin will be weakened: It will no longer be as easy for him to point to American democracy's flaws or to exploit them. Then, if he returns to his trolling as Comey predicted, he'll have to come up with something more sophisticated than what is essentially a cheap, simple influence campaign.

Help sometimes comes from enemies. Sometimes they provide it unwillingly. It takes a certain perceptiveness to recognize when that happens and accept the help.

Leonid Bershidsky is a Bloomberg View columnist. He was the founding editor of the Russian business daily Vedomosti and founded the opinion website Slon.ru.

This column was provided by Bloomberg News.