After the US launched strikes on Iran this week, Donald Trump said the fragile ceasefire he had co-signed just last month was over. He also reignited his threats to take Greenland, before leaving the Nato summit in Ankara, saying there was a lot of ‘love’ and ‘unity’ in the room. So how does anyone make progress with a leader choosing to relive a diplomatic Groundhog Day? Jonathan Freedland speaks to Susan Glasser of the New Yorker