Dude, the SPD are the social democrats allright. The CDU is what we call bürgerlich - think Republicans in the fifties. I was kinda making a joke about Merkel, but it's commonly agreed that she pulled the CDU way to the left, crushing the SPD in the process. Die Linke is split between the ex-GDR and the West: In the East, they're basically social democrats with a bit of leftist veneer, while in the West they're complete nutjobs. It's a shame they weren't crowded out by the SPD in the East in the 1990's.
Calling the CSU our tea party is wildly inaccurate, and calling Bavaria that is just plain weird. Bavaria may be closest to Texas: They have a strong regional identity, a conservative bend, a thing for populism, the occasional bout of separatism, and a disproportionally large say in federal matters. The CSU is the ruling party of Bavaria - they've been in power ever since the Bundesrepublik was founded, and their leaders are quite frequently compared to monarchs. They occasionally do stupid stuff and are stubborn enough to get their way in Berlin quite frequently, but they're certainly not abortion-banning, social-safety-net cutting Jesus freaks with an assault rifle boner.
BTW, if you want religious nuts, you need to go a bit further west - they're quite large in Baden-Württemberg. But politically they're unimportant.