The short answer to your question is that the United states currently has dysfunctional and ineffective governance, and you are seeing postal service performance drop as symptom of that. Additionally the pandemic also has an effect in that there are many postal workers who are either out sick or quarantined, so they are working with reduced staff.
Here’s a more detailed response:
Acronyms used in this response:
USPS (United Staes Postal Service): This is a SERVICE (not a business) provided by the U. S. Federal government.
UPS (United Parcel Service): a commercial shipping company
FEDEX (Federal Express): a commercial shipping company
The USPS is absolutely buried right now. There are a few reasons in addition to what was mentioned above (listed in no particular order):
1 - The current administration made an attempt to hamstring the USPS mid-summer to prevent mail in ballots from being counted in the election, and much of the problems caused by that (and there were many) have not yet been fixed.
2 - UPS and FEDEX, the primary commercial shippers in the U.S., placed limits on what volume of packages they would take from vendors this holiday season, both because they where getting overwhelmed and because most of us are shopping online and staying at home do to the pandemic, and because they have the responsibility for shipping distribution of the COVID-19 vaccines (FEDEX west coast, UPS east coast). This pushed much of the overflow of package delivery to the USPS, which is obligated by law to accept and deliver shipments, and cannot refuse them.
3 - In order to streamline their efficiency and services, UPS, FEDEX and other commercial shipping companies have over the past few years been delivering to local post offices (USPS) and letting the USPS do the “last mile” of delivery, since the USPS has to deliver to every address every day anyway. Amazon still does this as well to some degree, even though they have their own delivery folks. That portion of delivery, going door to door, to every household and business in the country is the least efficient part of the process, and the USPS is required by law to do that.
There were two days last week where no mail was delivered at all at my address. I am with 25 miles of two major east coast cities, not out in the sticks. Every delivery person I see, regardless of who they work for, looks utterly exhausted. The USPS workers look the worst. Many of them have been working 7 days a week for months at this point.
Our USPS delivery lady has made deliveries as late as nine at night, and she has taken mail for her route out of the post office after her shift is complete (because they are limited in how long they are allowed to work) to her personal car and delivered it anyway after hours because she felt bad we were not getting our mail, and she knew she would be even more buried the next day.
They are busting their asses. Have some patience. Things are really bad here. One American is dying about every minute.