Tracking USPS Signature Delivery mail- WTF???

In the last 6 weeks I have sent a package via USPS to flagstaff via Phoenix from Omaha. should be a straight shot,,,, eight days to flag.USPS said 2-3 days.
second time a package to Mesa arizona,,,,again 8 business days.They said 2-3 days
Third time we took it to fed ex. They delivered the morning of the third day.
My son heard thru the grapevine thru his employer that the USPS has an agreement with Amazon, giving them preference in shipping over the general public.. and if any employee speaks out, their job could come into question.
When I asked the lady at the counter that, I got a very nervous denial.