By Patricia Zengerle and Arshad Mohammed WASHINGTON (Reuters) – Despite threats from nearly three dozen Republican senators to thwart a revived Iran nuclear deal and the misgivings of some top Democrats, there is little chance the U.S. Congress can block a new accord if one comes to fruition. Lawmakers, congressional aides and former officials noted that Congress failed to quash the Joint Comprehensive Plan of Action (JCPOA), as the pact is titled, in 2015 when Republicans controlled both the House of Representatives and Senate. That is even less likely now that U.S. President Joe Biden’s fell…