Where are US nuclear weapons based in Europe and Turkey.
Over 100 US nuclear weapons are stationed in Europe under the NATO nuclear sharing agreement. Although the weapons are kept under control of the US who have to issue authorization codes for use the weapons would be flown by the Belgian, Dutch, German, Italian and Turkish air forces.
This is different from the situation in the UK where the nuclear weapons would be flown by the F-35A of the United States Airforce.
It is expected that it is intended to upgrade these nuclear weapons to the new B61-12 bombs.
There are several bases that have weapons storage facilities but, as far as we know, do not have nuclear weapons at the moment.
The situation in Turkey is unclear since then President Trump halted the sale of F-35s to Turkey because of its plans to acquire the Russian S-400 air-defense system. There are also security concerns due to the failed coup attempt in Turkey in July 2016.
For more information see: United States nuclear weapons, 2021; Bulletin of the Atomic Scientists Volume 77, 2021 (https://www.tandfonline.com/doi/full/10.1080/00963402.2020.1859865)