Obviously what goes on there is a whole other level, but even in the the rest of the world, we should realize that allowing someone to a live and work in a country without enfranchising them is an affront to democracy.
Historically we have actually benefited greatly from being a top destination for immigrants and aquired a lot of talent and may wish ultimately that someone else hadn't skimmed the cream while we make it hard.
I think that the primary requirements ought to be not being a criminal where you come from. People who go to school here ought to be offered citizenship at graduation others ought to wait a year. Even the folks that sneak over to work here illegally commit fewer crimes than natives as it stands.
Our birth rate is less than replacement and our density is a fraction of Europes.
Also, it gets complex when discussing illegal immigration. What if an immigrant is laying low for an extended time? Is it different if the host country looks the other way and doesn't really enforce the laws, because some sectors benefit from the cheaper labor?
In many other countries, like Australia and (I think?) Canada, for example, one can become a citizen after 4 years living and working in the country.
The US is kinda hypocritical in that on one hand there is a tacit desire to lord it over non-citizens, and in the other hand there is a vocal concern about exacerbating the glut of labor.
Well, an individual American can't have it both ways: you're either a net worker or net owner.