It would be highly unlikely that Thanos' Snap affected other dimensions. Firstly, we have no indication he even knew there were other dimensions; the closest we see to him seeing this is when he fights Strange. However, most of what Strange does there is just ordinary "magic".
Thanos is also correcting the universe to help save it and the life within it. If he were to affect some of the other dimensions which don't have direct life, for example, the Mirror Dimension, that might cause more problems than it solves.
Thanos: Little one, it's a simple calculus. This universe is finite, its resources finite. If life is left unchecked, life will cease to exist. It needs correction.
Avengers: Infinity War
Some of the dimensions are also more parallel worlds than life giving places, for example, the Astral and Mirror Dimensions. It wouldn't make sense to affect those in the first place as they don't harbour life.
And lastly, of the other dimensions we see only the Dark Dimension has any life within it (that I'm aware of) and that life is only Dormammu. It wouldn't make sense to kill him for the reasons of the Snap in the first place. And as he and the Dark Dimension exist outside of time it might not even be possible. Strange was only able to affect Dormammu in Doctor Strange because he took the Time Stone into the Dark Dimension. It's possible that the Time Stone can't affect it when outside of it and as such the might of the other 5 Infinity Stones is not enough for a full Snap.
I just want to tack a note on the end though that with Doctor Strange in the Multiverse of Madness coming out in a few years we might get a more explicit answer then. Even though it is likely to be set after Avengers: Endgame.