India, July 5 -- The 250th anniversary of American independence is colliding with a country gripped by political polarisation and a heat wave bearing down on millions of people across multiple states as celebrations get underway across the United States on Saturday.

The signing of the Declaration of Independence, one of history's most celebrated articulations of democratic ambitions, is being marked in myriad ways. President Donald Trump, set to take a central role in festivities, plans to speak on the National Mall in Washington ahead of what's being billed as a historically enormous fireworks show that will rain down over the nation's capital.

The president was in South Dakota at Mount Rushmore on Friday, where he delivered a dark spe...