Although Trump did not explicitly say it, his remarks were widely perceived to suggest that an attack occurred in Sweden.
"Sweden? Terror attack? What has he been smoking? Questions abound," former Swedish Prime Minister Carl Bildt wrote on Twitter.
The White House already faced criticism this month after it included an incident in the Swedish city of Malmö on its list of allegedly under-reported attacks. In October, arson caused smoke damage at an Iraqi community center in Malmö.
A judge, however, decided that there was no evidence for treating the incident as a "terror attack", months before the White House released the list that referred to the incident.
Sweden took in more refugees per capita than any other country in Europe at the height of the influx in 2015.
The country has long viewed itself as having a moral obligation to take in refugees from war-torn countries. But Sweden reached its limits as other EU neighbours refused to fulfill their commitments.
The influx of refugees has not come without problems in Sweden, but mainstream politicians and immigration experts say the criticism has been disproportionate. Last northern summer, Swedish embassies were tasked to counter rumours or false information on Sweden's experience with taking in large numbers of immigrants.
Speaking, one day before Trump's remarks, Henrik Selin of the Swedish Institute said there are "people whose political agenda suggests they would like to tell the story of countries not being able to receive that many refugees, who seem to want to exaggerate problems," according to Radio Sweden.
Although Sweden views itself as increasingly isolated in regard to its pro-immigration stance, the country found widespread cross-European support on social media.
"Dear @realDonaldTrump," Alexander Stubb, the former prime minister of Finland tweeted. "Sweden is immigration friendly, international & liberal. One of the most prosperous, richest, safest places on earth."
