Economist Mohamed El-Erian said investors had been optimistic about Trump's plans for de-regulation and lower taxes, while under-estimating the likelihood of a trade war.
He said the recent falls in the stock market, which started last week, reflect the adjustment of those bets.
European stocks closed lower on Monday, with France's CAC and the London FTSE indices both closing around 0.9% lower.
Susannah Streeter, head of money and markets at the stockbrokers Hargreaves Lansdown, said it was because of "unease around the impact of Trump tariffs".
She added that concerns over the US economy entering a recession is worrying investors.
Tesla shares fell about 8% on Monday, while tech stocks Nvidia and Meta were both down more than 4%.
"It takes a little time, but I think it should be great for us," he added. »
