Let bygones be bygones. American firms are champing at the bit to do business with Iran, set to emerge from more than three decades of sanctions to be lifted per last summer’s nuclear agreement. The potential is huge: The Islamic Republic’s market for electronics totaled $9.5 billion in 2014 and is expected to climb to $13 billion in four years. And then there’s petroleum, with General Electric’s oil services unit already investigating opportunities. A trade ban with some exceptions is still in place, but some in Congress predict relief could begin as early as January.