Initially (19th century) the US did not recognise copyright of foreign works. This is all about interests: when you are a net importer you want to make it easy

Initially (19th century) the US did not recognise copyright of foreign works. This is all about interests: when you are a net importer you want to make it easy and cheap to reproduce and use works. Buy once you start being an exporter you want your works protected, and that's a quid pro quo.