You can either roam on your UK SIM card or you can buy a local US SIM card upon your arrival in the States. … Best SIM Cards for Using Your Smartphone in the USA. Best USA SIM Card:Three Pay As You GoNetwork Coverage:99% US population coverageCompatibility:Works with most unlocked smartphones (including iPhone & Android)Best SIM Cards for Using Your Smartphone in the USA kenstechtips.com › index.php › best-sim-cards-for-usa