US military presence in Germany does not constitute “a huge part of [Germany’s] economy.” A welcome part, no doubt, but a very small part.
Conversely, the US would lose strategic bases close(r) to all the Mid East trouble spots. Including medical facilities used to treat troops wounded in Afghanistan etc.
The respective interests are pretty even, I’d say.
So what other weapon could Oboma use. I couldn't think of anything else he could use on them, but I'm not that well versed in German affairs - obviously.