The US is structured to promote loneliness.

If you want to fix it:

- More free public spaces (parks with benches, squares)

- More free public events and activities (free concerts, art installations, plays)

- Greater physical proximity (it's hard to make eye contact if everyone drives)

- Wealth distribution (create a society where one's value is not based on their net worth)

- Encourage days off for community service

In other words, provide socially-funded incentives for people to be close to one another physically and remove income as a measure of value.