Having nukes also keeps all others from attacking, for most second and third world powers the USians are the primary threat due to their very mobile military. B

Having nukes also keeps all others from attacking, for most second and third world powers the USians are the primary threat due to their very mobile military. But everyone has enemies, Britain and France feared a German resurgence after WW2 as well as a Soviet invasion of Western Europe. Israel fears it's neighbors and most muslim states. But in all cases, nukes are there to keep someone you fear from attacking. And various crises and practical problems causes even the British to not totally rely on US protection. E.g. the Suez crisis and the Falkland war showed them that they need their own military capabilities, because they cannot even rely on the US for support in "small stuff".