The slow death of Europe by 1000s of cuts. Put migrant activity on top of that and bye bye.
There is a posibility between "muh America is car-centric, and btw i am bad at driving so i hate driving" and "you have to walk even in bad wrarher and when you are 70, think about the climate bruh".
HN are a special kind of nonsense crowd.
I live in a pretty walkable Spanish city, and 70-year-olds are having a blast here. Even when they can no longer walk and they need to use various mobility devices, they can use the pedestrian infrastructure to move around the city and hang aroun the bars with their friends and families (and they do it basically every day, as far as I can tell). The same population in the US would be basically homebound.