Shipping-USPS vs. "OTHERS"

I have an order from John Knibbs (England) that is now 3 weeks overdue. The order was processed and shipped quickly from England (less than a week to arrive in Chicago). WHICHEVER "U.S." shipper was supposed to move it from Chicago to Arkansas has done nothing now for 3 weeks. No updates and NO LISTING of who the U.S. shipper is. I've contacted the seller to see if they can track on their end because nothing I've received lists WHO has it in Chicago now. Certainly frustrating.