While in some parts of the country I'm sure your right about the illegals, it's not that way, near me in central Indiana.
Around here, people I know only make 40 to 50 grand a year are in 250k homes with 2 sometimes 3 new vehicles, 3 kids, 150 dollar sneakers and Home theaters. Am I jealous.......nope not at all I didn't saddle myself with that kind of debt.
I didn't creatively finance, take out a second mortgage and then max out every credit card I received "free" in the mail.
This isn't about immigration, its about instant gratification.
It's about a lot of things that add up. You have to ask, what was the trigger here? Having lots of debt is not a bad thing *if* you can finance it. The question to ask is, why were people no longer able to finance their debt? It's a lot of different things which interact - some job losses here, some inflation there, some tax hikes someplace else, bad monetary and spending policies elsewhere, etc.