After spending the last three hours trying to fix this problem, I've successfully navigated the labyrinth that is Steam/Sega/Etc. to arrive here. 

Long story short, earlier tonight I launched Total War II: Rome. I've had 0 issues since 2015. The splash screen froze. Black screen and my mouse wouldn't move. So I do some googling. I do all the tricks (deleting folders, repairing files, etc.). It works somewhat, but then my DLC (Wrath of Sparta, Hannibal at the Gates, etc.) disappears. It freezes when I click the campaign. It's still in my library, but it won't let me play it. I uninstalled the game and reinstalled it. It worked, but the DLC was still not there. I tried the Grand Campaign, but when I try to adjust the aspect ratio of the graphics...it freezes again, and now I'm back to my splash screen being black and my mouse not moving.

I don't understand what is going on. My computer is up to date. No updates pending and none installed recently. Rome II is up to date. Steam and Sega support are useless. Anybody got any tips or tricks? I have no idea why this happened. Thank you