On PackageRadar website «Customs clearance complete» status means these statuses of USPS:
Tracking package of USPS
With the use of our tracking form you can easily check the status of your package. Also if you want to tracking USPS and get your package location updates to your e-mail, you can Register on our website.
USPS — is not the only postal service that you can track at PackageRadar. See full list of postal services available.