There’s no evidence that the universe is spinning. The observable universe is not a flat plane - we see galaxies in all directions and at all distances.

You may be thinking of our galaxy (the Milky Way) or even our solar system, which both rotate and as such are both somewhat flattened (the solar system much more so than the galaxy.)

But what’s happening here has little to do with that. If you imagine the closest distance that Earth gets to Mars as a yardstick, 3I/Atlas is about half that yardstick’s distance from Mars right now - much closer than Earth ever gets. It’s practically in Mars’ back yard.