According to Wikipedia (http://en.wikipedia.org/wiki/List_of_United_States_Army_inst...) US has 35 existing bases in Germany and has closed 207 (!) bases in the past. Some of the most important (strategic importance and size) are in Germany. To think that such a huge military presence has "exactly zero to do" with how freely German government can make decisions which would be contrary to the US interests is an illusion.
Its a financial risk. Germany could today tell the US to be out of the country by a set date and what could the US do? Likely at most point to contracts and treaty agreements and request negotiation. Does anyone really think the US could say no and get away with it?
Germany wants the money the bases bring and likely the perceived protection they present. If they didn't see the latter then the money point is key. How much does the US spend to maintain those bases and do they pay fees beyond that to have them?
As a Libertarian I would be more than happy seeing us out of every country that is peaceful. We have no real need to be there in this day and age with the ease at which power can be projected. I won't go into the question of being in certain other countries because of disagreements which led to war, declared or not.
West Germany is still occupied by US troops. The 2+4 treaty is !NOT! a peace treaty. Russians just withdraw their troops from east Germany. Take a look in the 2+4 contract, neither US troops nor US atom rockets are allowed in east Germany.
Each Chancellor has to sign a paper called Kanzlerakte, that he agrees, to give up sovereignty at lot of cases, e.e. intelligence, military.
There were plenty of shenanigans going on between the U.S. and German politicians in the early BRD days. But the scanned document everyone's been passing around purporting to refer to the so-called Kanzlerakte is obviously a fake.
I don't comment on the Kanzlerakte, it's obvious fake.
US barracks are not extraterritoriality zones, please cite your claim.
"US soldiers are not under German jurisdiction", this is only partly true. It's part of the "NATO-Truppenstatut". With Art. 19 Abs. 3 Satz 1 ZA (Zusatzabkommen) the foreign soldiers are part of German jurisdiction.