"You're assuming that the host country would actually allow the U.S. to make such a deployment over their skies/land."

No, actually I'm AFFIRMING that they let us do so. As part of the "rental agreement" we have the right to fly/hover/drive/pass through their land and air space. Otherwise the base would be pretty much useless

The bases in Germany were not ONLY placed there to keep peace, they were also placed there as tactical central locations.

You may be focused on the US economy, but that's tunnel-vision. We're in a global economy. Ensuring the stability of the EU (including Germany) helps stabilize the global economy and in turn ensures purchases of US items. Of course this breaks down when we talk about China, but that's not the focus of this discussion. ;)