The fact that it's not available in the United States is one issue, but there are several others at play. One cool aspect of the N95 is that is has the latest 3G capabilities, based on high-speed downlink packet access technology. Considering the multimedia uses of the phone, 3G is an essential component in making the overall experience of the device as good as possible. When high-speed downlink packet access isn't available, the N95 will fall back to EDGE 2.5G speeds in the GSM 850 band, which is technically compatible with certain U.S. wireless networks. It does not, however, have U.S. compatible 3G radio technology.
Furthermore, the European version of the N95 comes equipped with Wi-Fi, as do many other Nokia phones. While it's not Nokia's fault, any potential U.S. variant of the N95 is likely to be stripped of this feature as well.
What this boils down to is that if and when this device ever comes to the United States, it will leave U.S. consumers with a 2.5G radio in a phone that demands so much more.