Correct, .edu wasn't explicitly restricted to US institutions. But at that time, the entire ARPA-internet as a whole was only used by institutions that were do

Correct, .edu wasn't explicitly restricted to US institutions. But at that time, the entire ARPA-internet as a whole was only used by institutions that were doing something related to US government research. There wasn't really a thought to restrict domain usage for anyone, because the entire network was restricted access. The ARPA-internet wasn't open to the public, and things like websites and ISPs didn't exist. It was just a tool for researchers to use at work. The idea that .edu would ever accommodate a middle school teachers' union in France was not on anybody's radar.