Because of unbridled LEGAL immigration wages are suppressed and the average American is losing ground year over year. Stop immigration and watch the standard of living go back up.
Oh, yes, illegal immigration damaged us, too. As you say, by depressing wages for Americans but also helping to fuel the rise in healthcare & entitlements. Insurance companies simply passed on the cost of near-free healthcare passed out in hospital ERs to working Americans via higher policy premiums and co-pays.
Businesses fired Americans, instead preferring reduced-wage or off-the-books workers from the illegal population.
And our socialist-minded politicians wanted ever more indigents imported into America in the hopes of securing more votes.
Sigh.