At this point, considering how absolutely consistent the USA has been with extending copyright expirations when major IP is coming up to the deadline, I've come to assume that copyright is now perpetual.
The US doesn't even make a show of it anymore. Mickey Mouse must be protected at all costs in perpetuity, all the benefits of expiring copyrights to the population at large be damned.
TFRs (temporary flight restrictions) are intended for short-term events like air shows and missile launches, but Disney's TFR has been in effect since 2003.
Trademark is cleverly entwined into this as well. Since Mickey is Disney's trademark mascot, the law is in favor of protecting any work containing Mickey ad infinitum.
The US doesn't even make a show of it anymore. Mickey Mouse must be protected at all costs in perpetuity, all the benefits of expiring copyrights to the population at large be damned.