LONDON — It was a revolt against elite complacency, an almost palpable shock to conventional wisdom and conventional politics. Opponents could barely comprehend the poll-confounding news. This was June in Britain, not November in America, and the upset was the British decision to leave the European Union.

The election of Donald J. Trump as America’s 45th president has strong parallels to the British decision, known as “Brexit,” but the impact will be much bigger, in Europe and the world.

Mr. Trump’s victory was hailed by European far-right leaders, including the Hungarian prime minister, Viktor Orban. And there were immediate concerns about how the anti-elitist surge will affect other European votes, and how a Trump presidency might respond to a post-Brexit Britain.

One main reason for the surprise at the polls was the participation of people who in the past had rarely voted. That is a lesson that could echo all over Europe, where the Italians will hold a constitutional referendum next month, the Austrians will vote for president and the French are about to hold a presidential primary among center-right candidates — and as France and Germany gear up for national elections next year.