If I understand correctly, the US have long been capable of a retaliatory strike against the USSR / Russia that is powerful enough to nearly completely destroy the target state. (If I'm wrong on that, could you point me to links that explain why?)
Why then does the US choose to place strategic nuclear forces in Europe? The value of the deterrent cannot increase much, once the near-destruction is assured. On the other hand, the risk to the US significantly increases, since the Russians/Soviets have a shorter warning for missiles launched from Europe, and therefore may be pressured to act quickly, leading to a higher risk of an accidental full-scale nuclear exchange. (E.g., the Russians may need to rely on the satellite instead of the radar detection, and the satellites have higher false positives.)