I think about this all the time. One of my gripes about movies and shows that play with the parallel universe theme is that things are only slightly different in the alternate universe.
In the show Fringe, all the same main characters exist in the alternate universe but their personalities are just slightly different.
In the show Counterpart, Howard Silk is a meek toe-the-line company employee in one universe but a fairly aggressive secret agency employee in the other. He is happily married in one, divorced in the other.
In The Man in the High Castle, the Axis powers win World War II and America is occupied by German and Japanese forces.
These plotlines make for good entertainment storytelling but the reality is that these universes wouldn’t even look remotely similar. Entire generations of people from one universe wouldn’t even exist in another. Country lines would be unrecognizable — or maybe there wouldn’t be countries at all. Maybe a different type of civilization would have emerged.
The Butterfly Effect starring Ashton Kutcher is probably my favorite example of this (while not being a great film in general). Kutcher’s character discovers that by reading his childhood journals he can travel back in time. So he attempts to make changes in the past to protect his friends from some of the trauma they’ve experienced in their lives. Of course, everything he does (even something as simple as saying yes or no in an isolated conversation) produces unintended results. Sometimes a friend ends up not existing at all in the present timeline or a different friend ends up suffering in a new way.
Watching this film made me realize, like you’ve said here, that “it is so hard to become us.” And once you realize how many unique combinations of yes’s and no’s it took to become us, you really do become aware of how it is “hard to continue to be us.”
What decision will I make today that will completely change the trajectory of my life? Will I even know that I’ve made it?