Reuters: Most oil drillers are fretting after crude prices fell 70 percent since last July, but a group of Oklahoma oilmen pin much of the blame for their plunging profits on an unlikely culprit: Canada. Producers led by driller Harold Hamm have asked local authorities, including Oklahoma’s attorney general, to investigate whether Canada — the largest oil supplier to the United States — is selling crude at prices below production costs from its vast oil sands reserves. The Oklahoma …