This is not business as usual, no matter what the US said about Saddam, Assad or Noriega in the past. Those look the same, but they are most assuredly not the same in practice.
While there are multiple documented calls by the US for regime change, they:
were generally frowned upon when the US first started getting into the habit of doing so.
concerned small tinpot dictatorships, not Russia, a major nuclear power.
not a country whom the world has a deep vested interest in seeing to effect a change of course and withdraw, without being able to coerce in doing so.
With Saddam and all, the US was mostly acting on its own, for its own purposes. There was no coalition that needed to be held together and most of the world didn't particularly care, one way or the other if the US proceeded or stopped.
As Anthony Zurcher, the BBC US correspondent says Why Biden's off-script remarks about Putin are so dangerous:
The speed with which the US issued its "clarification" - later echoed by Mr Blinken - suggests the US understands the danger inherent in Mr Biden's words.
There's a line between condemning a nation's leader - the sometimes overheated rhetoric of diplomacy - and calling for his removal. It was a line both the Americans and the Soviets respected even at the height of the Cold War. And it is a line that Mr Biden had apparently crossed.
"Regime change" is something powerful countries are accused of imposing on weaker ones - not what one nuclear-armed nation demands of another.
By Sunday, even some US allies were attempting to distance themselves from Mr Biden's remarks.
Biden, has, on the whole, done a very commendable job of bringing together the coalition against Russia. He's also been very good at reminding the younger generations of the inherent constraints brought on by nuclear MAD theory. He's preemptively outed some of their planned intentions. He's even been good at not upping the US DEFCON when Russia upped theirs earlier in the crisis.
Then he does this. After calling Putin a war criminal the week before.
The fact that many of us will feel that he is right does not make saying it publicly any less of a gaffe. He got elected to a position which requires keeping a tight lid on one's mouth when necessary.
Another indication that this was not normal practice is that Biden had to publicly disown his own statement:
"But I want to make it clear: I wasn’t then nor am I now articulating a policy change," Biden said. "I was expressing moral outrage that I feel, and I make no apologies for it."
Now, if this was just like previous POTUS regime change calls, why did he have to do that?
p.s. I am not questioning Biden's competence, which I otherwise would rate highly in this crisis. Nor should anyone put words into my mouth about his age - a criticism often raised by Trump who often looked way more doddery himself.