The map you reference seems to show the larger pipelines of various types. It would be helpful to have a color reference guide. It is not obvious to me what the map shows.

This is a map of oil refined product pipelines:

This is a map of crude pipelines:

Natural gas pipelines go pretty much everywhere, except New England has minimal coverage.

Maps for the various products can be found by scrolling down this page under "pipeline coverage".

Regarding pipelines crossing the Canada border, they go both ways. The tar sands that Canada processes are too thick to send through pipelines to the US to be processed, without first being diluted with some lighter oil. In order for this to happen, the US needs to send lighter oil north, by pipeline, to use as a dilutant. Most of the tars sands oil is refined in this country, I believe. Some of the refined product then gets sent back to Canada.