Okay we are talking about two different things here. First of all H1B only applies to white collar workers with at least a 4 year college degree. As for the undocumented workers, you have to take into account that they usually do the work that local workers are not too keen on doing. As for the taxes, they usually pay the taxes as they are deducted by the employer. If anything, these workers pay more since they cannot file for a refund.

It's interesting how you refer to the foreign workers as leeches because they are anything but that. They pay social security tax and unemployment taxes just as domestic workers do, except they are not entitled any benefits from either unless they become permanent residents. Not to mention the 3-4K visa fees that the employer has to pay for their visa renewal every three years, don't you think that's accounted for in their package. Also a large part of the foreign workforce are people who went to school at some stage in this country, guess how much they "contributed" to your financial aid packages.