Final answer:
The St. Lawrence Seaway has created a cheaper way to ship U.S. and Canadian products around the world, opening up access to international markets.
Step-by-step explanation:
The St. Lawrence Seaway has had a significant advantage on trade by creating a cheaper way to ship U.S. and Canadian products around the world. This seaway connects the Great Lakes to the Atlantic Ocean through the St. Lawrence River, allowing goods to be transported efficiently and economically. It has opened up access to international markets and facilitated trade between the U.S., Canada, and other countries.