One of the biggest blunders was decommissioning the SR-71...IMHO. Perfectly good aircraft with years left in service life and it was ditched with the preposterous excuse that it was “Too expensive to operate”.
“Too expensive to operate” = “We already have a replacement”.
Special mechanics, special pilots/training, and most expensive - special fuel delivered by aerial tankers in faraway places. If you wanted to track the SR-71 you might follow the KC-135 tanker carrying its special fuel and wait for the blackbird to show up. Knowing this, I suspect the AF would have a whole fleet of KC-135's full of the special fuel in the air all over the world, with only one or two actually meeting up with an SR-71. Expensive enough yet?
Also, I believe improvements in sensing and anti-aircraft missile tech made it increasingly dangerous to fly over hostile territory. Maybe there's still a need for recon, but is a manned aircraft still needed for this job?
OTOH I have to agree that decommissioning the SR-71 was a mistake. Beautiful aircraft, unique design, still the fastest thing in the air. It should have been kept flying, but for pure research into the science of speed. If they quit trying to keep it so secret, a lot of the expense would go away.
I have heard a rumor that there was a particular USAF General who pushed to scrap the SR-71 program because he was bitter about washing out of the pilot selection process for SR-71s early in his career. When he achieved the rank and billet with the authority, he recommended to civilian leadership to end the program.
Don’t know if it is true.