Associated Press: The first firm evidence of what likely caused the disastrous Gulf of Mexico oil blowout — a devastating sequence of equipment failures — drives home a central unsettling point about America’s oil industry: key safety features at tens of thousands of U.S. offshore rigs are barely regulated. Wednesday’s hearings by congressional and administration panels in Washington and in Louisiana laid out a checklist of unseen breakdowns on largely unregulated aspects of well safety that appear …