The question arises as to why alternate universes are created in the first place. One theory regarding potential universes is that of splitting universes. This suggests that every time a decision is made another universe is created. Reality splits into two universes, identical except that each represents a different possible result of the decision. Cause and effect can work not only within their original reality but also across these alternate realities.
Alternate universes are exactly that, alternate.
They are not the same. A cause in one universe does not have any connection to another universe once it has been formed. As previously stated, a cause can have another universe as its effect but that is where the association ends. Once a new reality is created, it should continue on its own as an alternative to the original. The original also progresses as if the alternate does not exist.