Final answer:
Canada forms the North borders of the United States along the St. Lawrence river.
Step-by-step explanation:
The country that forms the North borders of the United States along the St. Lawrence river is Canada. Canada shares a border with the United States and stretches from the Atlantic Ocean in the east to the Pacific Ocean in the west. The St. Lawrence river forms part of this border between the two countries.
Learn more about Borders between the United States and Canada