Once Trumputin finalize their non-aggression pact shortly, there will be no reason to keep American troops in Germany or indeed in Europe in general. All these troops who are sitting on their buttock eating bon-bons can then be repositioned for an attack on Iran where they can actually earn their pay doing what they are supposed to be paid for.
In Germany proper, there will be some initial economic discomfort because of the loss of monetary input both directly from the troops and providing for the supplies and support of the military structure but their economy is fairly strong and they will survive and thrive, once again becoming the European powerhouse.
Old bases can be either converted to additional housing, airports, sporting venues etc. which will also assist in the economic recovery from the loss of US dollars. Another possibility will be the renting some of these bases to the Russians for their military purposes.
American tourism is also likely to decrease both because family will no longer be visiting servicemen who are now in the Iraq staging area and this decrease is likely to persist as the US isolationism policies intensify.
This US isolationism will come on quickly because it is actually favored by all sides. In the US there will be an attitude of not needing to visit other parts of the world because they are not us, beneath us and don’t deserve us or our money and the rest of the world will be happy to accommodate us and have us stay home and keep our noses out of their business.