When USPS tracking says departed USPS regional facility it means that the package has departed a sorting facility that is closer to your location.
The package first goes through the origin facility and then to a regional facility and then could go through another origin facility before it reaches your local post office.
When the package gets to your state where a sorting facility is then it will get delivered to your door or post office within a few days or even the next day.
Whenever I see the USPS tracking says my package has arrived in the state where I am at the sorting facility then the next day the package arrives.
The USPS tracking does not update all that often so it's a waste of time to check too often.