France and the UK have nukes precisely because they did not believe that a country would be willing to risk total destruction to protect another country.
It's been very important to the Nato stance to have multiple nuclear armed states, it made Soviet calculations extremely difficult. With the USA leaving the alliance I think that either a joint Euro bomb needs to be developed or Germany needs to acquire one. Perhaps a polite fiction (continuing the current one by the USA) of France providing nukes for German, Dutch, Danish and Polish war planes could be used.