"Collision" is a bit of a misnomer when we talk about galaxies. As large as stars are, the matter in galaxies is still so sparse because stars are so far apart. I saw some maths about the coming collision between the Milky Way and Andromeda and the number of projected collisions is like less than 10 (IIRC).

Now I'm sure it would be highly disruptive and there'd be localized catastrophe but it's important to remember how large the distances in space really are.