By Kanishka Singh and Enas AlashrayWASHINGTON/CAIRO, , April 3 (Reuters) - President Donald Trump said the U.S. "hasn't even started destroying what's left in Iran", reiterating vows to increase the ferocity of attacks on its infrastructure, as dozens of countries sought ways to restart vital energy shipments through the Strait of Hormuz.Nearly five weeks after it started with a joint U.S.-Israeli aerial assault, the war in Iran continues to spread chaos across the region and roil financial mark...