Scott Adams has a great post on immigration.
A better immigration policy would be to make the U.S. as inviting as possible so everyone wants in. Then choose the most worthy applicants based on how much they would contribute to the economy, or how attractive they are. And obviously all applicants would have to pass a physical exam so they don't burden the healthcare system.
As Scott says, improving our schools and environment and crime rates benefits everyone.
My favorite quote from the post, though:
The U.S. can't match Canada in friendliness, crime rates, personal freedom, or the environment. But no immigrant wants to walk around in a snow suit trying to understand French either.
Really, they just need a red velvet rope and a big dude in a black t-shirt working the door at the airports – and a nice side effect is that no one is getting in with a sneaker bomb (or sneakers period).