U.S. President Donald Trump and British Prime Minister May seem concerned with security and terrorism issues. They could lessen these issues considerably by following the common sense of the latest attacker - on Manchester. He is quoted as saying that he was acting because Britain had attacked Libya, Syria and other Muslims. Revenge. 

It makes sense. One country attacks another and citizens and friends of the country that was attacked can be expected to strike back. All the countries which have been attacked, including US, France, Germany, Britain, Canada have troops fighting in the Middle East area. So it should have been no surprise that they were attacked. 

Thus if countries took their troops out of the area, revenge strikes should decrease. No western nation has an obvious interest in that area, so little would be lost, and a lot of lives saved.

May and Trump could spend their time healing their very fractured countries, caused by Brexit and Trump.