This thread has some tips on pre-paid SIM cards for use in the USA: [WayBack] Telefonie en mobiel internet in de VS deel 2 – Pagina 9 – AllesAmerika.com Forum
This seems to be one of the few allowing for hotspot/tethering use: [WayBack] Arieli Mobile Unlimited + Tethering Data plan | Arieli Mobile – Prepaid USA SIM Card wireless provider
Via: [WayBack] T-Mobile vergroot databundels Travel & Surf-passen voor buiten EU – Tablets en telefoons – Nieuws – Tweakers
–jeroen