Given the amount of American military infrastructure that was in the UK (and other allies) during the cold war any attack on the United States would almost certainly have included missile and bomber attacks on the allies.

Also with the fact that most Western European countries are quite small and densely populated compared to the United States and the Soviet Union the carnage here would have been indescribable (although if you want a feeling for what a "best case" attack might have been like feel free to watch Threads).