Which band will use in USA and Europe ?

In Europe GSM900 is a very coomon cellular system, the band is Rx:(935-960MHz) and Tx:(890-915MHz).
In the states The PCS1900 is the common band, it is a GSM system but on a different frequency band (1850-1910 MHz and 1930-1990)

correct ..
in europe gsm900, gsm1800
in usa gsm1900
for exact spect you can check specs of some triple band gsm phones e.g. ericsson t39 or motorola timeport xxx

in usa only GSM1900 ?

I suspect that as the demand on the mobile systems goes up changes will be made to increase the efficiency. The first thing will probably be the conversion of the bands that use analog FM to digital.