the default to north America happens if an address cannot be found by the goole geocoder.
looking at the source code of your page many of the street addresses are giving an address range, for example:
street: 'Via delle Milizie 3 - 00192 Roma',
this is not a valid street address, the street address should be only:
Via delle Milizie 3
make sure the street addresses stored in the database are correct.
you can change where the default is by finding the following code in the map js file:
map.setCenter(new GLatLng(30, -98), 3);
and change the coordinates to another location.