Upvote:3
Single Ticket: If your flights are on a single booking, your bags get will get checked through to the final destination. You just need to walk off the arriving plane and walk over to your departure gate. If this is a Lufthansa Ticket, you most likely arrive and depart both in Concourse L.
Two Tickets: If your flights are on separate bookings, you will have to clear immigration, claim your bags, exit landside, go to the check-in counter of your departing airline, drop of your bag and grab a boarding pass, go through security again (it's only called TSA in the US) and exit immigration, and then, finally, go to your gate.
I have read that if I have to recheck my luggage that I may need to obtain a transit visa.
No. US citizens don't need a Visa for Schengen entry (in most cases) and you are not entering Germany in the first place