Delivery standards are being loosened in many countries due to significant reduction of non-package mail during the last decade, this is not US-specific. E.g.

Delivery standards are being loosened in many countries due to significant reduction of non-package mail during the last decade, this is not US-specific. E.g. here in Finland the standard stamped mail service has been reduced from mostly 1 day to 4 days, and in many areas they are only being delivered on every other business day (so one carrier alternates between two routes, I think). There are also significant yearly increases in stamp prices, which US has not yet seen I believe. These non-US measures were also briefly explored in USPS Office of Inspector General report RISC-WP-20-004 in 2020 (https://www.uspsoig.gov/sites/default/files/document-library-files/2020/RISC-WP-20-004.pdf https://www.uspsoig.gov/sites/default/files/document-library...).