Stimulating my curiosity

I've been ignoring as much as I can Obama's upcoming stimulus plan. I just know that the more I learn of it, the more my head will feel like it's going to explode. And I also know that it will be impossible for me to ignore all the unsavory details as the program gets implemented.

But there's a few things that have been puzzling me as I tangentially learn of his plan.

First, just as a general proposition, now that we're poor how is spending money on infrastructure projects that did not seem worthwhile when we thought we were rich a good idea? This seems a bit like losing your job and deciding to start work on the addition to your house that you felt you couldn't afford when you were employed. Sure, the plan is to put an office in there and start making real money but maybe that's just stupid?

Second, isn't construction one of those "jobs Americans won't do"? Wasn't that what we heard a couple of summers ago when we were told that the amnesty was imperative? That any effort to staunch the flow of millions of illegal immigrants would be disastrous for the construction industry? How is giving money to illegal immigrants to send home in remittances going to stimulate our economy?

Third, doesn't construction take massive amounts of steel and concrete and things of that nature? But don't we import most of that dirty stuff from China now? How is paying China to make steel for Mexicans to install in projects that aren't good investments going to help again?

Lastly, why is Obama calling for economic stimulus at all? Yes, I get that he wants the economy to be better, but wasn't he the one telling us that our consumerist ways were unsustainable and insulting to the rest of the world? Well, congratulations, we are no longer consuming nearly as much as were. But somehow that's now bad too? Kind of a damned-if-you-do, damned-if-you-don't thing?

But prob. I'm just missing something fundamental.