I don't know of any specific Steelers bars in Munich. But you may want to try the Champions American sports bar in City Center Marriott.
Other than that, many bars with "Sky" TV would probably pick it up. You may want to check out an Irish / English pub as they would most likely pick up the British Sky feed which would be in English (British English) whereas the German Sky feed would most likely be in Deutsch.
Either way, I would call ahead to check as local start time in Munich will be 00:30 (I think), so you'll need to find a bar that is staying open until 03:30 or so...
GOOD LUCK and Go Steelers!