You may need to update the settings for US operators.
You can find more information on the site.

If you're using a camper van or caravan, it's best to add an external aerial as the walls of the vehicle prevent the best reception.
You need an aerial with 2 cables and pay attention to the type of connectors.

No doubt it's an American product. Here are the networks supported :
4G: FDD-LTE: B1/B3/B5/B7/B8/B20/B28 (2100/1800/850/2600/900/800/700 MHz)
TDD-LTE: B38/B40/B41 (2600/2300/2500 MHz)
3G: DC-HSPA+/HSPA/UMTS: B1/B5/B8 (2100/850/900 MHz)