(FILES) US Presidnt Donald Trump greets Canadian Prime Minister Justin Trudeau at the White House in Washington, DC, on June 20, 2019. Donald Trump has not yet returned to the White House but is already thrusting himself to the front of international stage as he once again shatters diplomatic niceties. As only the second former president elected to a non-consecutive term, Trump is at least a known quantity to world leaders. Even his knack for unpredictable behavior is predictable. (Photo by NICHOLAS KAMM / AFP) (Photo by NICHOLAS KAMM/AFP via Getty Images)