You’re talking about the Sonny Bono Copyright Term Extension Act aka the Mickey Mouse Protection Act?
Claiming that was due to foreign pressure was just scapegoating / misdirection from its supporters.
The US forced all sorts of copyright extensions on the international community back then (including DMCA-style DRM protections).
The support section of the Wikipedia page lists the main lobbyists for the bill. They are all US based, and Disney started lobbying for it in 1990 (the year after the US was brought into compliance with the Berne convention).
https://en.m.wikipedia.org/wiki/Copyright_Term_Extension_Act