Instead of sending it down to Texas refineries through a secure and stable pipleline, The oil will travel over successive pristine rugged mountain ranges, through an active serious earthquake zone to be loaded on leaky ships in the environmentally sensitive coastal waters of British Columbia, which will transport the oil through fog-shrouded channels to the open ocean to Chinese poorly-regulated ports through substandard pipelines to refineries in polluted China and then......be burned releasing the same CO2 into the atmosphere.
Meantime,we will continue to buy heavy crude from corrupt Venezuelan poorly-regulated oil fields around filthy Lake Maracaibo and ship the crude in leaky vessels across the Hurricane-prone Gulf of Mexico waters to refineries in Texas, after which it will .....be burned and release CO2 into the atmosphere.
From EIA.gov: Canada remained the largest exporter of total petroleum to the United States in January; exporting 3,205 thousand barrels per day. The second largest exporter of total petroleum was Saudi Arabia with 1,444 thousand barrels per day.
If you think this administration's motives have anything to do with saving the environment, I will sell you some beach front property in the TX Hill Country.
Canada has a conservative government interested in growing the economy and exploiting natural resources. The US, not so much.