What If... Captain Carter Were the First Avenger? - S1-E1
Deliberate mistake: When Peggy and Steve are studying the map where the 107th Army division is held captive, the names on the map are nonsensical names that do not even follow German spelling or standards for place names ("Farfignugen," "Dädtenorth," and "Rosskjhberg," for instance). Most of them are also reused, appearing several times on the same map. This is most likely done deliberately so as to avoid any resemblance to real places, but still looks out of place and illogical. (00:11:27)
What If... Captain Carter Were the First Avenger? - S1-E1
Other mistake: The premise of the first episode is flawed; "a single choice" should make the difference, the choice being identified as Ms. Carter not leaving the room to get in the observation booth. But in the normal timeline the booth is exactly where all the other characters were. In this reality everyone else is downstairs, with the German spy that inexplicably sets the bomb early. If anything, it's his bizarre, suicidal choice that matters.
Suggested correction: Except it was her decision to not leave the room that delayed the procedure and gave Heinz Kruger the chance to attack. And with her in the room, she is now given the chance to volunteer to take the serum.
How did her staying delay the procedure? Besides, in OTL the spy only triggered the bomb after he saw the procedure succeed, to know it works before stealing it.
What If... Captain Carter Were the First Avenger? - S1-E1
Factual error: When Stark starts telling about the Tesseract, the colonel shows surprise that Nazis were in Norway. Peggy answers with "Close. HYDRA." The scene is set in 1943, and Norway had been occupied by Nazi Germany for three years already. Them being in Tønsberg should not come as a great surprise to an Allied commander. (00:07:10)
Suggested correction: I feel like this falls under the "Not a mistake because it's an alternate universe" umbrella. We're in an entirely different universe with a different timeline in this episode.
The show also makes a point that the only difference should be the minor choices or events befalling the MCU characters, and how these minor things have huge consequences for them, basically creating a new alternate timeline. Basic world history before these events is not affected by the new timeline.
Basic, unaltered world history does not apply with this because we are talking about an alternate WWII from the beginning. One with Schmitt/Red Skull as propaganda minister of Hitler, Hydra superseding the SS, super soldier serum, Stark tech, the Tesseract, etc. It is not WWII as we know it, even without the "what if."
What If... Captain Carter Were the First Avenger? - S1-E1
Factual error: In the intro, we are shown how Nazi Germany spreads across Europe - but after showing Denmark being conquered, it is shown to start spreading across Sweden. Sweden was never occupied by the Germans in WWII.
Suggested correction: I feel like this falls under the "Not a mistake because it's an alternate universe" umbrella. We're in an entirely different universe with a different timeline in this episode.
The show also makes a point that the only difference should be the minor choices or events befalling the MCU characters, and how these minor things have huge consequences for them, basically creating a new, alternate timeline. Basic world history before these events is not affected by the new timeline.
Suggested correction: The black spot spreading is not representing territory physically conquered by the Nazis, but more of their sphere of influence expanding. It is a steady spread and not a true representation of the war's progression. You can notice how Switzerland is also covered by the black, even though it was neutral during the war. Nor was Italy conquered, but their ally instead.