[jcranmer]

First, the plurality of illegal immigrants in the US are people who entered the country legally but have overstayed their visas. There's not a lot of sneaking into a different person's country to do work.

Second, there is no "legal line" for immigration. The closest you get is that some visas where conversion to a permanent residency (green card) has an annual quota that is so heavily oversubscribed that there is a permanent backlog which stretches, in the most extreme cases, to over 20 years long.

Third, even when you're dealing with the legal immigration processes, that process is a bureaucratic hell that I don't wish on anybody. If you don't have anybody willing to descend into paperwork hell for you, then there is no way for you to immigrate to the US.