You wouldn’t see any billionaires.

There are near 800 billionaires in the USA. Assuming all only have $1 billion dollars and it is all invested, applying the “4% rule” gives a sustainable $40 million each per year. With $10 million to personally spend, that gives $24 billion a year for charity and public works.

I failed to find a list of the costs to solve various issues. Homelessness could be solved in a couple years.

The numbers provided are just a starting place. Many problems are extremely expensive. Actually working to solve them would help.