Avengers: Endgame - Everything That Changes If The Heroes Steal The Infinity Stones From The Past

12. No Advanced SHIELD Weaponry (& A Different Avengers?)

It wouldn't be entirely right to suggest that the Avengers wouldn't have been formed were it not for Loki using the Tesseract to invade Earth, because The Avengers Initiative predated that. Ultimately, the World Security Council scrapped the plans in favour of using weaponry to defend Earth against alien invasions like the New Mexico incident that saw the Destroyer follow Thor to Earth.

The problem with that, of course, is that the weapons wouldn't be possible without the Tesseract falling into SHIELDS' hands after Howard Stark rescues it (and Cap) from his icy "grave." Without that alternative, the World Security Council would be forced to persist with the Avengers Initiative.

Though, with other major events leading up to the Avengers' formation dependent on the Tesseract, the Council and SHIELD may not have gone with the candidates they ended up hiring in desperation. Tony Stark, in particular, wouldn't have made it, since he was rejected at the second round of vetos and Thor wouldn't have become an Avenger at all.

Again, that's why you don't mess with the Tesseract too early.