Not Greece, we tried that one before.
The truth of the matter is that Britain, Iceland, Spain, Italy, and Turkey are the ONLY European countries in NATO that are REALLY of much strategic importance to us; Portugal, Denmark (including Greenland) and Norway might possibly also be added to that list, but they are much more marginal -- the main importance with them is to not fall into hostile hands. All of these provide direct access by sea and avoid any serious overflight problems. Spain, Italy, and Turkey especially are all much closer to places where our forces will be likely to be needed. Britain and Iceland are essential for naval security in the N. Atlantic, with Norway, Denmark and Portugal being of secondary importance.
Poland and the Czech Republic become important if "keeping the Russians out of Europe" is an important strategic objective for us. I'm not sure at this point if it really is. "Keeping the French/German axis from linking up with the Russians and dominating Europe" might be a more realistic and important strategic objective.
I see absolutely no good reason why we should continue to need any US forces in Germany.