The movement of these bases and US air wings to eastern Europe puts them closer to the southwest asia/Iran hot spot..and more importantly, the treasties being negotiated will not require the US to get permission every time we want to stage out of them..
Yu may be too young to remember the US raid on Libya..but France refused us overflight , so the F-111's from Britan had to take the long way around..necessetating an extra 12 hours and 3 mid air refuelings before the strike..the afteraction reports believe that the fatigue/stress of that mission way well have contributed to the loss of the US aircrews....so, never again..
The restructuring is already decided and there´s nothing Merkel or any other German politician could do about it. But these bases aren´t moving to the East. Some eastern European countries get one or two bases, but half of the withdrawed troops move back to the US. Last time Germany refused overflight rights for US aircraft was May 7th 1945 ;-). Even during the Iraq war there was no doubt that Germany fulfills its obligations as an ally. Everything else would have meant the end of NATO. Don´t worry, 35,000 GI´s will remain here, mostly on Airbases. And they´re welcome. :-)