I don't think the country was ready for Trump yet in 2012. I also think the GOP would be less likely to get fully behind him then, especially after a bitterly contested primary against Romney that goes all the way to the convention. OP doesn't give a reason why Obama retired, so absent information otherwise, I'm gonna assume it has nothing to do with scandal or anything, or that anything went catastrophically wrong compared to our timeline. Maybe he just decides to pull a Polk and retire after one term. Maybe Michelle convinces him to give it up. And I don't think Hillary beating Biden in the primaries should be read into too much either; she was also still an active part of the administration in 2012, after all, and was more popular in her own right at the time. It was already assumed she, not Biden, would be Obama's successor.
I think the map would basically be the same as real 2012, give or take FL, OH, and IA. Bitterness over Romney's defeat combined with distaste for Trump may also cause a McMullin type Mormon candidate to either win Utah outright or spoil it for Trump.
Oh, and if Hillary was the incumbent after winning in 2008, she definitely wins. In that case, it could feasibly be something like this:
The post-2008 mass exodus of the WWC from the Democratic Party would not have happened in this timeline, as they would have gotten their candidate (Hillary, ironic as that seems today). Maybe she even wins states like KY and WV in 2008, and Trump's populism could be enough to poach those from her, but I doubt much else.
