What happens if US withdrawal from the world stage is irreversible?

While Whitehall may be distracted by Brexit, President Trump has proven to be a master primarily in the politics of distraction. His announcement on 6th December to recognise Jerusalem as the capital of Israel and move the US Embassy to the city is a case in point, and seems to have been done primarily to appease his base, with little understanding or care about the political ramifications. Suffice it to say, so far, this president does not appear to have the ability, or the temperament, to tackle issues of global significance.