There’s alread three pipelines coming south from Alberta...Express, Enbridge & Keystone (phase 1). Oil is still going to flow south with or without Keystone XL
Yes, there are other crude oil pipelines from Canada to the US. But they all terminate in the mostly land-locked and crude-short Midwest (PADD III). Keystone would move cheap crude all the way to Houston, where it would trash the structure of world crude prices. Crude markets are already glutted and yet more crude flowing into the refining complex around Houston would force the Saudis and Russians to further reduce output to keep prices up.
Make no mistake about this: The problem with Keystone has nothing to do with environmental concerns. The real issue is from a US national security standpoint. It would put severe downward pressure on crude oil market prices, which the US has been successfully propping up for more than a decade as part of multi-pronged economic warfare against the Chinese. All the enviro yammering is just window dressing. It is geopolitics, national security and it is China.