I think we have to be honest when attempting to ascribe attitudes to the historical Jesus. The word "xenos" in Matthew 25:35 means "stranger," as Sister correctly translates. Jesus' own attitude toward foreigners, however, appears to have been more complex (cf. the encounter with the Syro-Phoenician woman in  Mark 7: "It is not right to take the food of the children and throw it to the dogs" and the encounter with the Samaritan woman in John 4). 
I think we have to accept the fact that we feel called to extend hospitality to foreigners by many values we hold dear as Christians and as Americans, but recourse to the historical Jesus is not as helpful as we might like it to be.