TORONTO — The busiest crossing on the U.S.-Canada land border was blockaded Tuesday as the demonstrations against vaccine mandates that have paralyzed Canada’s capital spread to a crucial trade artery, while inspiring similar protests from Europe to Australia.

The Ambassador Bridge, which links Windsor, Ontario, to Detroit, was “temporarily closed” for passengers and commercial traffic, authorities on both sides of the border said Tuesday, though Windsor police said “limited traffic” was being allowed into the United States. The 1.6-mile suspension bridge is an important trade link, particularly for the region’s auto industry. It also connects families, friends and essential workers, including Canadian nurses who work in Detroit-area hospitals.