We didn't "invite the Americans", as RetroCop said @ 19.47.
They became our allies when Germany declared war on the USA in alignment with the Japanese after Pearl Harbor. This was the start of the so-called "special relationship", because up to that point, the Americans had no idea that "ULTRA" existed, and we were obliged to share intelligence with them.
There was absolutely no "special relationship" before, during or after, WW1, where the Americans entered the war as a result of conflict with Mexico, who were allied to Germany, so Germany declared war on the USA in 1917. Absolute nothing to do with the UK.
During the 1930's, the USA had drawn up plans to declare war on Great Britain, which would have started with the invasion of Canada and continued with the invasion of British territory in the Carribean.
The Dieppe raid was not a total failure becuase British marines siezed all the secret German documents and Enigma machines from the intelligence headquarters, which was located in a large hotel by the harbour wall.
I'm pleased that the President is paying tribute to all the brave people who fought against Hitler and
Nazi-ism, and anyone protesting against his visit should stop and think about the reason for him being here, which is nothing to do with all the gubbins I've heard and read, about Trump this week.