People often find arguments to support their feelings and point of view. Immigration tends to mean cultural change; the introduction of new ways of doing things, and a challenge to the status quo. IMO conservatives are on the balance more anti-immigration than liberals simply because they are conservative and skeptical of change by nature. I wish it were simply a matter of holding beliefs that can be countered by data, but I think the goal posts tend to move to preserve the stance. -Not for all, but for conservatives as a voting block.
Ya after I moved out of the city I found the people here ( mainly conservative white people) just couldn't comprehend how they could possibly fit other cultures in. Mind you they have no problem stuffing their faces with sushi but I find people who don't grow up in a multicultural area have a much harder time making space for others. It's like only child syndrome but for cultures.
I think it might be an age thing, on both sides, and I've seen it both from smaller towns as well as cities. Younger people seem to be more receptive to immigrants and younger immigrants tend to be more open to American culture. Older people, both as American born citizens as well as immigrants, aren't hostile or anything. They just seem to prefer to not interact. I'm not a fan of city living, I bitch and moan about a lot of things. One of the things I do love about it though? The number of immigrants is pretty cool to see, and I love it when they open their own restaurants. One of my favorite places is this hole in the wall Greek place and every night I eat there, the kids are at the table doing their homework while mom and dad run their business. It's a cliche phrase at this point, but when I think of "The American Dream" I think that scenario fits in nicely.