I have a nokia 6600 in uk , can I use it in usa with a local sim

You need to Unlock the Phone from the Network lock ,to use with other GSM Network Sim card,you cannot use other Network Sim in the Phone it locked means ,So Insert Sim in USA it accept means you can use any GSM Network Card,because it's Unlocked,It's Not accept means it's Locked Phone,You need to Unlock it,Get the code from here
Simpleunlocking.com and Unlock it.