SummaryIn his feud with Trump, Musk announces "America Party" Musk plans challenges to Republican incumbents Trump calls third party "ridiculous," says US is built for two-party system Investment firm delays launch of Tesla ETF WASHINGTON, July 6 (Reuters) - President Donald Trump called Elon Musk's plans to form a new political party "ridiculous," saying Musk could have fun with his new project but that the United States functions best under a two-party system.A day after Musk escalated his feud with Trump and announced the formation of a new U.S. political party, the Republican president was asked about it before boarding...