Who would now be king had the United States been founded as a monarchy?
Since George Washington had an older half brother and a younger full brother, ultimately there were four possible succession paths. Two of the four paths, with male-only heirs, converge into one heir—Paul Emery Washington, 82, of San Antonio, Texas—making him the strongest candidate for king today. Paul Emery Washington also has a son, Bill, who he affectionately calls "Prince William."
Paul Emery Washington was a regional manager at Certain-Teed Corp., a manufacturer and distributor of wholesale building materials for 40 years. The company was headquartered in Valley Forge, Pa., where coincidentally General Washington and his army camped during the difficult winter of 1778-79. [Link]