The volatile, dramatic US presidential race between Kamala Harris and Donald Trump headed to an unpredictable finish Tuesday, with millions of Americans casting their votes in one of the tightest elections of modern times. The result — which may be known overnight or not for days — will bring major consequences, either making Harris the first woman in arguably the world’s most powerful job or handing power back to Trump and his nationalist “America First” agenda. As voters formed long lines across the country, several bomb threats were reported at polling stations, while police at the US Cap…