we push away chatty strangers in the United States
Where? I've lived on the coasts, I live in the Midwest, that has not been my experience aside from anti-social persons.Tourist areas of large cities are like this. LinkedIn connections are like this. Other than that, people are delighted when you speak to them for the most part.
If nothing else, the nerves and flashbulb memories overwrite old nerves and flashbulb memories.
It depends strongly on the city, and became more pronounced since covid.
Seattle is the worst. They call it the "seattle freeze." The San Francisco Bay Area became almost as bad in covid.
The south is still friendly. Austin is incredibly friendly with strangers. Miami has strong stranger vibe. NYC is still alive, too.