The spit/warhawk thing is actually quite believable, although for the most part I believe American volunteers to have flown US planes under the lend/lease agreement. BUT.... Benny boy was wayyyyyyy too tall to be a fighter pilot, he would have been a buffer by default in the US Army Air Corp.
What part of the Spit/P40 part was believable?
The only 40 drivers to have any real success at Pearl Harbor were Welch and Taylor. Their fight sure didn't involve getting Zeros to collide with each other over the airfield

Did American pilots fly with the RAF? Sure. Not a one got back in the USAAF in time for Pearl Harbor. Many were accepted into the USAAF afterwards. Many chose to stay with the RAF/RCAF instead.
Again, no single pilot flew Spits with the RAF, then P40s at Pearl, then B25s with Doolittle.
As for suspending my disbelief. Again if they'd called it anything but Pearl Harbor, I probably could have. One of my all time favorite WW2 aviation movies is a wartime film called "Air Force" about the mythical B17D "Mary Ann. She happens to fly into the attack at Pearl Harbor. Drops in on Wake Island for a look and then makes it into the Philippines where she is shot down, rebuilt and leads the attack to sink a big Japanese attack fleet shooting down tens of Japanese fighters along the way.
Not an ounce of truth in the entire movie, but they also didn't name it to imply it was tied to any certain event as the makers of "Pearl Harbor" did. Very easy to suspend my disbelief and enjoy the airplanes in "Air Force".