Public transit is a great example. Pretty much every attempt to privatize transit worldwide has resulted in, if not failure and subsequent deprivatization, at least higher prices and worse service for the people using the service.

The interstate highway system, which replaced a complex system of partially privately owned roads, is another.

In most countries, healthcare is another great example. And arguably education as well - public schooling produces generally pretty good results worldwide for not that much money per student, and outside the US, higher education is often public and incredible value for money.