I think what you're talking about is basically what Age of Ultron was about. Banner, and particularly, Stark were looking to create Ultron as a "suit of armour around the world".
The world was reacting in different ways with SHIELD building the helicarrier army under the guise of global protection, and Von Strucker seems to be looking to try and join an invasion for personal benefit. But the ting is, a guy like Stark is who the world would be looking too for help with creating a global initiave, but he's a polarizing character and already one of the Avengers, so we only really see the end game of what is assumed to be Earthly panic, and that is "what will Tony Stark do to save us?" and it seems to be Stark's whole motivation for continuing to be involved with the Avengers at all.
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