US President Donald Trump on Friday congratulated UK Prime Minister Boris Johnson on his election victory, saying their two countries were now free to strike a "massive" new trade deal."Congratulations to Boris Johnson on his great WIN!", Trump tweeted."Britain and the United States will now be free to strike a massive new Trade Deal after BREXIT. This deal has the potential to be far bigger and more lucrative than any deal that could be made with the E.U. Celebrate Boris!"