[qyph]

From your article: > The United States became a party in 1989.

The person you are responding to is writing about American Copyright. https://en.wikipedia.org/wiki/Copyright_law_of_the_United_St.... The first american copyright law is from 1790, which does in fact predate the bern convention, and our life of the author plus 50 years rule is from the copyright act of 1976, 13 years before the US ratified the bern convention.

So yes, it is an 'American thing' as are all issues of law in the US. And if you think that this kind of convention is meaningfully binding, just checkout the history of the US and other major powers with regards to various other international treaties, like the ICC https://en.wikipedia.org/wiki/International_Criminal_Court.