USPS package tracking question.?

I know things have been diffrent with Covid19 and all and im not complaining, but im trying to understand what happens when a package shipped from over seas gets to the united states what happens next? Does the tracking number change? How long does it stay in whatever state it landed in before moving to the next destination? For example my package was Shipped from China and last known location was California. Ive been unable to get any new info on where it is now. Im not complaining, i know USPS workers and drivers are understaff im just trying to get an idea of what the process is for international to US shipping steps and timing are.

Thanks