Birthdays can be complicated. They might bring about mixed emotions, introspection, regret, hope. Now, for a birthday about to be observed by 350 million people, it’s no surprise that America’s big two-five-o is feeling a little fraught. There’s anxiety about what the anniversary means and tension between the two organizations at the center of the semiquincentennial, the bipartisan America250 and the President Donald Trump-aligned Freedom 250. L…