When the USPS tracking information has updated and says arrived at USPS facility it means that the package has arrived at a USPS facility which usually means a sorting facility.
When the package arrives at the USPS sorting facility then it is being sorting or has been sorted and then as it leaves the USPS sorting facility the USPS tracking should then update to say that it's departed the USPS sorting facility.
It can take until midnight before the USPS tracking updates to say it departed the USPS sorting facility so be patient.
USPS tracking does not update often and checking too often will not show any different results.
I just check my USPS tracking number after midnight and then it updates.
Once the USPS tracking says arrived at destination facility or something similar then it's getting closer to you.
It can also be a day or so before the USPS tracking updates but during that time it should say that the package is in transit to the next destination or is moving within the USPS network.