During the decades after World War II, a growing share of U.S. and Canadian women participated in the workforce, boosting household incomes and national production, while opening new opportunities for women themselves.

Then in the late 1990s, something changed. Female workforce participation began slipping in the U.S. while it kept marching higher in Canada. By 2016, 74.3% of U.S. women between the ages of 25 and 54 were working or looking for work, compared with 82.2% in Canada, according to Organization for Economic Co-operation...