The USCCB has launched an initiative to try to change public opinion, or at least Catholic opinion, on immigrants.[1] Immigrants help our country and society in a number of ways, from doing the hard jobs, to enriching our culture (on a superficial note, would we have the wealth of food types without them?). The bishops are highlighting the problems in the immigration system, from bias against them among us, to the difficulty getting into this country, a difficulty that some claim causes the illegal immigration. Additionally, the ID mess strikes immigrants particularly hard. We use the same few IDs (birth certificate, drivers license, social security number) for pretty much everything, and an immigrant can have trouble getting providing these things.
[1] http://www.catholicherald.com/cns/cns05/immigration.htm