Passport and Visa Requirements for Germany:
If you are a US citizen: You do not need a visa to travel to Germany, only a valid US passport. Make sure that your passport does not expire before the end of your visit in Germany.
You can stay in Germany for vacation or a business trip up to 90 days.
If you are not a US citizen: See this list of the Federal Foreign Office and check if you need to apply for a visa to travel to Germany.