WASHINGTON—The Trump administration dropped plans to add a citizenship question to the 2020 census form, a turnaround after days of defiant statements following last week’s Supreme Court decision to halt the query.

“We can confirm that the decision has been made to print the 2020 decennial census questionnaire without a citizenship question, and that the printer has been instructed to begin the printing process,” a Justice Department attorney told lawyers for New York state and the American Civil Liberties Union by email Tuesday...