This pipeline only passes through the US and back to Canada
Not really, it supplies 40% of Michigan’s propane which is a heating fuel outside the urban areas and about 10% of the State’s crude.
In addition, it gets sent to Sarnia Ontario, and after refining it, some re-crosses the border as gasoline.
The same also takes place at the Nanticoke refinery on the North Shore of Lake Erie, it gets trucked across the border at Buffalo and Lewiston.