On May 7th it was announced to the public that he US was pulling out of the Iran Nuclear Deal. Why? Because Donald Trump is displeased with Iran’s actions; he believes Iran is not following the rules set up as part of the deal.
But in doing so, he’s going against the other countries who are a part of the deal: United Kingdom, Russia, France, China and Germany. They disagree that Iran is doing anything out of line, and therefore wanted the US to stay a part of the deal.