The U.S. is relying the most in four decades on oil from the Americas as the shale revolution reduces imports from the Persian Gulf and Africa . Countries outside North, Central and South America supplied the smallest portion of foreign crude in August to the U.S. in government records dating back to 1973. Surging production in Canada and the U.S. has reduced the need for cargoes of light oil, with the remaining imports of heavy crude more likely to be from Mexico or Venezuela than Nigeria or Saudi Arabia. The shift is another sign of how the North American energy revolution is affecting some suppliers more than others. OPEC members, including Saudi Arabia, Venezuela and Nigeria, meet tomorrow in Vienna to decide whether to cut output in an effort to prop up prices that have fallen 31 percent since June. U.S. refiners built the capacity to use heavy crude, […]