PEW: Most Americans (55%) consider the oil spill in the Gulf of Mexico to be a major environmental disaster, but a majority (54%) also favors increasing offshore drilling in U.S. waters. In the wake of the spill, however, support for more offshore drilling is down. Fully 68% favored increased drilling in April 2009 and 63% wanted to drill more in February 2010. The drop off in support has come from Democrats and independents; pro-drilling sentiment feel by 13 points among both groups, and is now …