>But somehow “I” only experience only one of them.
Using the example from the other comment, "You" are the stream and not a drop of water in it.
In other words, you are not an entity with unique identity that traverse the tree of possibilities. You are part of the tree, actually, part of a branch. The branch's existence and your existence implies each other. Like your hand's existence and your existence imply each other. Your hand could not have existed without you (a similar looking one could. but it wouldn't be yours). And you without your hand (you could have had a different hand, but that wouldn't be "you" (which also includes the hand))
Using the example from the other comment, "You" are the stream and not a drop of water in it.
In other words, you are not an entity with unique identity that traverse the tree of possibilities. You are part of the tree, actually, part of a branch. The branch's existence and your existence implies each other. Like your hand's existence and your existence imply each other. Your hand could not have existed without you (a similar looking one could. but it wouldn't be yours). And you without your hand (you could have had a different hand, but that wouldn't be "you" (which also includes the hand))