President Donald Trump's ambassador to Italy has angered residents of his host country with plans to bring his $450 million superyacht to Venice during one of the city's most significant annual festivals, in a trip he has branded "coastal diplomacy."Billionaire Tilman Fertitta, a hospitality mogul who owns the NBA's Houston Rockets, began a weeks-long tour of the Italian coast on June 13 in Civitavecchia near Rome to mark America's 250th anniver…