Canada on Monday is lifting its prohibition on Americans crossing the border to shop, vacation or visit, but the United States is keeping similar restrictions in place for Canadians, part of a bumpy return to normalcy from COVID-19 travel bans.

U.S. citizens and legal permanent residents must be both fully vaccinated and test negative for COVID-19 within three days to get across one of the world’s longest and busiest land borders. Travelers also must fill out a detailed on application on the arriveCAN app before crossing.

The Canada Border Services Agency said travelers should plan for th...