You're getting downvoted because you're insensitive. Yes, it's true that there are immigrant-intent visas and non-immigrant-intent visas. There are fewer people who get the right one, and even fewer people who really know what they want. Maybe they come to the US on a TN visa and think, "hey, I like this place, I think I want to live here". Now they're an illegal alien based on your definition. Similarly, there are people that get immigrant intent visas and don't like the country all that much, and never bother to apply for permanent residency. Both are fine and reasonable decisions. If there weren't fixed numbers of visas, people might make the right choice, but since there are, they decide "I'll get in and sort it out later." (Hint: get a lawyer if this is you. It can be sorted out, but it isn't trivial.)
Anyway, as an American, I don't really see the point of restricting entry to the country. Nobody is going to steal our jobs. Incoming criminals are going to have quite a bit of trouble with the local criminals, which are quite numerous. It will all work itself out.
It's not like there's free medicine or food given out to everyone in the country, so if you're here, you're own your own. The government will send a fire truck to put out a fire in your home, and we have some roads. That's it for government assistance.
You are also an atypical worker. Less-skilled labor faces a much greater potential threat from uncontrolled immigration than you do. Also, many potential immigrants might decide to live in the US based on mistaken, outdated perceptions of opportunity and social mobility, but later wouldn't have the financial resources to relocate again if reality didn't meet expectations.
Emergency medical care is provided freely, and has its costs, as well as public education. Also you can't discount the risk of turf wars and violence with the "native" population, especially during times of economic stress or other instability.
Don't get me wrong; i'm all for immigration streamlining and reform, as well as equal legal protections for all people regardless of citizenship status. But immigration control remains a complex, multifaceted issue, that does not necessarily lend itself well to fully idealistic, ideologically pure solutions. Even the most liberal (or libertarian) of European countries have border control and non-trivial, exclusive requirements for immigration, with many policies and requirements being even more restrictive and byzantine than those of the US.
Anyway, as an American, I don't really see the point of restricting entry to the country. Nobody is going to steal our jobs. Incoming criminals are going to have quite a bit of trouble with the local criminals, which are quite numerous. It will all work itself out.
It's not like there's free medicine or food given out to everyone in the country, so if you're here, you're own your own. The government will send a fire truck to put out a fire in your home, and we have some roads. That's it for government assistance.
Anyway </rant>. Come steal my job.