There are actually about 7 or 8. Most prominent is the St Lawrence.
The Country that shares the southern Border with the US is Canada.
Canada and Mexico
Two countries share a border with the United States. To the north, the US shares a border with Canada. To the south, the US shares a border with Mexico.
Canada does
The Yukon River crosses the Canada-US border, but does not form part of it.
Canada and Mexico
Both Canada and Mexico border the US.
Michigan
Yukon Territory
Mexico shares its northern border with the USA.
"Does Canada border the US?" Yes, it's the only country it borders. ================================================ Oops! Not so fast! Canada also shares a border with Denmark. The international boundary runs across Hans Island.
Alaska, as it shares a border with Canada that extends for about 1,538 miles.