More Words, Deeper Hole

The reporting by Murrow on CBS radio from London during the Blitz did much to make Churchill admired in the U.S. Then after the war he became the first Cold Warrior, which appealed to many in the U.S. as well. (The English people on the other hand knew Churchill, and when peace finally came they voted him out of office because they weren't in the mood for preserving the Empire when it came down to it.)

As to the percentages note, Churchill does seem to have regretted it, but the facts on the ground (i.e. the military forces) were really what mattered and that's all Stalin cared about.