It’s hard to say. What would happen if Germany demanded that US forces leave? Germany undoubtedly has the right to do this. I don’t think anyone can say what would happen with any confidence, as it’s quite an outlandish scenario. My guess is that, ultimately, US forces would leave, NATO would collapse, and relations between the US and Germany would decline precipitously. But hey, actions have consequences. This does not mean that Germany cannot get rid of US forces if it wants to; it just means that it doesn’t want to because it would be a bad idea.