Following world war 1, United States didn't want to mess with European affairs because they understood how bad the war was and didn't want to participate in it again. That's why when Wilson wanted to join the League of Nations they declined and the US remained on its own.
The public goods means government goods and services because the market has failed and the market has not provided them. Sometimes the advantage of not allowing the market is our advantage.
In the case of the police, national defense and public educations, they argue some time that privately providing these services is less desirable for some reason.
Public goods are collectively consumed financial products such as highway, sanitation and school and national defenses service, police and fire protections.
