Theoretically, the USA has an almost endless supply of wealth including an overwhelming supply of natural resources to include property of vast forests, mining claims, farmlands, tourist properties, fishing grounds, building sites for industry and residential use, etc. We own rivers, lakes, and beaches.
And whether anyone wants to acknowledge this or not, we own debt from other countries, whose asses we saved in World War 2. Without the hundreds of thousands of lives we sacrificed/lost in the Pacific war, China would not exist today. It would have been a colony of Japan, if the Japs had not wiped them out entirely.
European countries are along the same line - England, France, Denmark, etc.