,There's a key line from the Ancient One that is being overlooked in the discussion of time travel mechanics. She says "The Infinity Stones create what you experience as the flow of time. Remove one of the stones and that flow splits."
To me this says that you can only create a divergent timeline by removing a stone. Otherwise you have always been part of the past and your actions always happened.
How does this apply in the movie? A new 2012 timeline was created when they removed the mind and time stone. In this timeline Loki escapes with the Space stone. There is also divergent 1970 and Thor 2 timelines, but both of those are Extremely simmilar to the original since Cap returned the stones with minimal disruptions. The Last divergent timeline is the one created in 2014 by removing the Power stone, this is the one that is now missing Thanos and is probably a really chill place to live.
After returning the stones Cap travels back to about 1950. He removes no stones so no new timeline was created. He was always there in the past in the original timeline. That's why he was able to live to the present without having to use the pad to get back to the right universe.
There's only one problem, where did the new shield come from? Simple, it's new. Probably had Black Panther make a new one after the unsnap. It's not identical there are some small design details on the points of the star that are new I think.
