I'm curious to know what the sky would look like without any other galaxies out there. How much do other galaxies factor into the stars we see? Does the Milky Way account for most of them? Would the night sky look normal? Or would it be very empty?
I feel sure this is a repeat, but couldn't immediately find it. The only things in the night sky we can see (with the naked eye) that are not part of our own Galaxy are (on a good night) the Andromeda galaxy and the Large and small Magellanic clouds. Every individual star brighter than $V=6$ and visible to the naked eye is in the Milky Way.
So it would hardly look any different.
It wouldn't be too apparent, but there are a few objects that you can see in good viewing conditions with the naked eye that would disappear.
Here they are in order of brightness. I marked the objects in a reddish color.
The Large Magellanic Cloud, apparent magnitude 0.9, located in the constellation Dorado. Only visible from the southern hemisphere.
The Small Magellanic Cloud, apparent magnitude 2.7, located in the constellation Tucana. Only visible from the southern hemisphere.
The Andromeda Galaxy, apparent magnitude 3.4, located in the constellation Andromeda.
And that's it. Seriously. Sure, there are a few others, but they're exceedingly difficult to see.