The simple answer is that those bases aren't considered US territory and do not constitute annexation, and in most cases are there by invitation, such as to defend against the other, worse, hegemon.

(Some exceptions apply for e.g. the Chagossians)

> Why don't the US retreat into their internationally recognized borders?

Mostly they were allowed there by the government of the place.

They are criticised for the exceptions.

> GDP largely based on death and destruction

For all the flaws of the USA, this is not really what their GDP is "based on", though perhaps one could say that functionally they hide conscription by giving many unemployed men a Hobson's choice of signing up vs. going hungry.

As the current situation in Middle East shows, these military bases loose their military function very fast in 21st century.

Crazy comparison, military bases based on political agreements has nothing to do with invading a country.