The Keystone XL pipeline debate seems to me to be much ado about nothing (or at least very little).
On the one hand, the major environmental issue is that extracting oil from the Arctic tar sands has severe adverse environmental consequences because of the release of harmful gases into the atmosphere. Not building the pipeline will not stop development of the tar sands. The pipeline question is really one of the safest, most environmentally responsible means of transporting what the oil. US citizens can protest, but banning the extraction is really a Canadian issue.
At the right price, the oil is worth extracting. Wells for extracting oil from tar sands usually have a productive life of 30-40 years, during which oil producers expect oil's price to fluctuate considerably. If US consumers dramatically reduced their oil consumption (e.g., reduce miles drive per year to 5,000 per person and only buy vehicles that have an estimated miles per gallon in excess of 40), global demand for petroleum products might drop substantially. Then oil companies would have far less of an incentive (perhaps no incentive!) to develop costly sources of oil, such as the Artic tar sands. Changes in US lifestyles might ripple around the world, given both the US's influence on many other cultures and the profitability of selling gas efficient vehicles in multiple markets.
On the other hand, the major economic issue related to the Keystone XL pipeline appears to be creation of a few thousand short-term jobs, mostly for construction workers (Glen Kessler, "Will Keystone XL pipeline create 42,000 ‘new’ jobs?" Washington Post, January 6, 2015). This project is too small to be a lasting catalyst for economic revival. The project's effects are likely to be similar to those of the Alaskan pipeline, which provided a similar, short-term economic boost to the Alaskan economy but did not have significant long-term consequences for the state (NB: I'm discussing the pipeline and not the exploitation of Arctic oil fields!).
Consequently, I found Ryan Lizza's suggestion in The New Yorker that the Keystone XL pipeline represented an opportunity for Obama to make a deal with the Republican controlled Congress Intriguing. Lizza suggested that a deal might allow the Republicans to claim an economic victory in terms of job creation and Obama to claim an environmental victory by trading the pipeline for Congress approving a much more significant environmental issue such as EPA guidelines for carbon emissions. His article is worth reading ("The Keystone XL Test: Can Obama Make a Deal?" The New Yorker, January 9, 2015) and an idea Obama and our Senators and Representatives in DC should support.