Now I want to build a CubeSat that will point a laser pointer at different population centers as it passes around the earth. E.g. this pass of North America you choose LA, then NYC, then Houston, then Chicago... so you can see it streak by in the sky.

My rough estimation is you could create a spot 2 miles across with a standard laser pointer at 400 miles high. Maybe you could use a different kind that would have a little more spread. And you'd have even more if you weren't beaming directly downwards -- maybe you could point it at 45 degrees or more with a powerful laser and get nice coverage.