That is a very apples to oranges comparison. For example, in the case of Iraq (a terrible moral mistake and embarrassment for the US in my opinion), the President, his administration, and most of the media really believed the Iraqi's were making weapons of mass destruction. They were extremely biased, and they suppressed the counter argument. All bad, I am not trying to defend it, but not the same. The other historical examples you give are all different in their own way. But in almost every case (except Watergate) they involve some reputable people who in good faith believed what they were saying.
No knowledgeable person believes what Trump is saying about mail in ballots. I don't think he believes it. This is really different.
Except the his administration part. I dont think cheney and rumsfeld believed it. It was largely manufactured. And the “counter arguments” werent really arguments. The administrations own advisors said the uranium couldnt have been sold.
And the tubes they barely clung to as proof were heavily contested by just as many that believed it internally. Thats not actionable intel.
And when the advisor outed his own reports publicly, his wifes career was ended by being outed.
It was malicous from within from specific participants, but not necessarily the president. Unvetted, unactionable intel was used as cover. Nothing more.
Bushes negligence was not being throrough and surrounding himself and empowering the absolutely wrong people. But the buck still stopped with him.
No knowledgeable person believes what Trump is saying about mail in ballots. I don't think he believes it. This is really different.