Earlier quoted context omitted.
If it was wildly successful, how did we end up with tons of private competitors with a large market share (FedEx, UPS, DHL, OnTrac, etc). The U.S. Is one of the only countries where the state run postal service isn't sufficient. In Switzerland, for example, there is only the Swiss Post. Most countries, to my knowledge, operate with just one major postal network.
There are many niches within the general category of "post". USPS's focus (and monopoly) is on first-class and bulk mail. How much cost/time does it cost Swiss Post to ship a package 4000km ? It's at least 3x the price of USPS: https://www.post.ch/en/private/a-z-of-subjects/prices-sendin...
I read your comment as 'Given USPS can send a package over 4000km in the same country, let's compare that with international charges in Switzerland'¹. Is that correct? Because that would be a liiiittle bit misleading in my world and I'd like to compare Swiss international charges with a USPS delivery from New York to Reykjavik please.
① Apologies if that isn't the case. But 4000km just felt too close to the east coast to west coast distance.