I'm an open-borders libertarian...The enormous costs to 3rd-worlders of living in their home countries is so large that all domestic problems pale in comparison.
To whatever extent you are a liberal, classical or otherwise, a global-villagist, or a humanitarian, you must think that the restriction of Haitians to Haiti, North Koreans to North Korea, and Africans to Africa is the biggest (top 3, say) tragedy facing the world today.
Haitians in the US make dozens (GDP/capita = $100/month vs. minimum wage~=$1,250/mo), or sometimes hundredfold (A little above the 80th %ile of US Household income= $10,000/month) increases in their own standards of living (income), and oftentimes are able to remit enough back to Haiti to make a family of twelve substantially less poverty-stricken.
North Korea is probably worse, as is Zimbabwe, where not only is there poverty, but also persistent (van Creveldian) low level conflict/war.
The net gain to allowing any 1 person from any of those places to immigrate into the US is phenomenally positive.
Now...The counter-argument, recently taken up by my favorite econ/statistics-jedi, Tino:
- Low skill immigrants are bad for the US, even though high skill ones aren't.
- (Low Skill) Immigrants are bad for freedom.
- Low skill Haitian immigration may be too costly
However...there's a further argument for immigration that I've never heard anyone use. Similarity breeds trust, which breeds higher government activity. A significant portion of the Scandanavian/Euro- welfare state exists because (1) countries are relatively small (the smaller in population the more welfare-ish), and (2) they are tremendously homogenous. Notice that the issue being taken up in the Netherlands, Austria, and causing pretty substantial unhappiness throughout France and Ireland as well. Heck...the extent to which a US neighborhood is racially/culturally homogenous does a pretty good job (I can't find the study) of predicting the levels of social trust in the neighborhood.
To decrease government activity, decrease social trust by increasing immigration. Also, it's tremendously good for the immigrants. FWIW, the other no-majority countries (switzerland, singapore, hong kong) all seem to do pretty well for themselves, usually by means of low-government activity.
UPDATE: I was called out for sloppiness by Andrew. Fair.
Switzerland is famously multi-lingual, but German is 3/4 of the language spoken. Partial fail.
- Defense: the number of immigrants in Switzerland who are not citizens may impact this substantially.
Singapore -- 3/4 ethnic Chinese. Partial fail.
- Defenses: immigrants constitute 1/3 the population, and also, Chinese is a suite of cultures...it's like saying that Italians and Swedes are pretty much the same.