WASHINGTON—President Trump’s 2017 tax cuts reduced the U.S. tax burden to one of the lowest among major world economies, according to a Thursday report by an intergovernmental organization.

U.S. tax burdens dropped by the largest amount among those countries in 2018, and the U.S. now has lower taxes than all but three countries in the Organization for Economic Cooperation and Development, the report said.

Driven by the federal tax cut that Congress and Mr. Trump enacted at the end of 2017, U.S. taxes at all levels of government fell to 24.3% of gross domestic product in 2018, down from 26.8% a year earlier and 25.9% in 2016.

That 2.5 percentage-point drop was only the fourth time since 1995 that any country’s tax burden has declined by at least that much in one year outside of the financial crisis, according to OECD, an intergovernmental economic organization with 36 member countries including the U.S.

The steepness of the decline stemmed partly from an increase in 2017, when a one-time tax from the 2017 law was counted as revenue that year.