Ahh, immigration. It divides Republicans and Democrats alike, so we can get a break from the usual culture wars.
My mother emigrated from England to Canada. I emigrated from Canada to the US. My paternal grandfather emigrated from Ireland to Canada. Speaking of Canada, my birthplace has an interesting take on immigration. They select for wealth and entrepreneurial productivity, a very mercenary approach that favors job growth in Canada and minimizes disruption.
The US has a different approach, and a different problem. Immigrants are selected for a willingness to work in harsh conditions for low wages (often associated with illegal status), for professional rather than entrepreneurial skills and for family bonds to citizens (the latter is where I came in). The consequence is economic benefits to immigrants and their employers, a mildly positive benefit to the nation as a whole, and probably negative effects on some US workers (per a recent Krugman/DeLong set of essays). The calculus is complex; if illegal aliens didn't harvest US crops either robots would do the work or the crops wouldn't be grown here any longer. On the other hand roofers would be paid more -- that work has to be done and can't be outsourced. Nannies would be paid much, much more, but many women and a few men would switch to day care or stop working.
Besides the economic complexities, there are interesting legal and cultural issues. To what extent is the US owned by its citizens -- vs. for example, the foreigners who increasingly own our bonds, our stocks and our land? What special privileges do America's owners demand as a benefit of ownership? Do we owners want to do something to boost wages and employment of less skilled workers, or do we want to boost overall wealth and lessen the impact of the aging boomers?
If it were up to me, I'd take a hard look at what Canada does -- maximize the economic benefits of the immigrant stream. I'd also want to get some real data on the impact on less skilled US workers; I'd probably choose "protection" of some domains. I would also look at a range of measures to favor and increase english language skills; I came from a nation divided by language (Quebec) and I think that's a very bad idea for the US. Lastly, I think a lot of labor intensive agriculture probably doesn't make sense for the US any more.