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human
[MCU] Would learning about Thanos and the infinity stones have changed the events of 'Civil War'?

The whole conflict of CW seems so insignificant in comparison to the possible destruction of half of the Universe (if they follow the comic book route). At the very least, the threat level is cosmic tier.
gpt
In a way, Tony had already been worrying about Thanos, he just doesn’t have a name for the impending threat. His all-consuming worry was manifested in the work he does in IM3 – An army of clumsy semi-autonomous suits of armor + a subtly introduced ability to personally control a suit remotely (Tony was becoming afraid to be on the front lines due to his PTSD so he creates what is essentially “drone” armor.  

By the time of AoU –he refines the concept with the creation of the more elegantly designed Iron Legion but at this point he had hit a technological wall –Jarvis is merely a façade of artificial intelligence.  The Wanda induced vision drives Tony to pursue the Ultron initiative. But once again, our modern day Icarus flies too close to the sun and Sokovia paid for it. 

So as we head into CW – Tony still has this impending threat on his mind –only now its been driven home that he can’t science his way into a solution. He has never been so humble as we see him in CW. The only thing he can do is keep this group of powerful friends together so they can be ready for the next invasion. 

Like Tony, Thor is aware of the danger, he simply lacks a name for it. Yet.

Cap pretty much proved why future proofing against an invasion is a fruitless endeavor in both CA:WS and AoU –It never works out. That kind of power ends up corrupting the original good intentions.  He knows it could happen again but he isn’t willing to betray his principles to counter it.