(The Conversation) — As the United States marks the 250th anniversary of its independence, old questions have returned about who belongs and whose religious practices are truly protected in the country. At the start of the year, an arson attack significantly damaged the oldest synagogue in Mississippi. Two days later, local officials in Oklahoma rejected a proposal to build a mosque after opponents declared Islam “hostile to our Constitution.” A Texas GOP congressman complained on social media that a Hindu festival was a “third world” practice. These incidents come amid resurgent claims that the United States is a Christian nation. All this has happened even as President Donald Trump has emphasized a particular idea of religious liberty throughout his second term.…