What country lies south of Detroit, Michigan?

If you take the Ambassador Bridge south from Detroit, it will take you directly into Windsor, Ontario, the only major Canadian city south of the U.S. Windsor is home to, among other things, an engine plant for Ford. Detroiters had been able to pop down to Windsor and do duty-free shopping. But with tariffs, is that still the case? Will our current international relationship mess with the Ford plant? If Canada became a state…