There is no reason for us, born citizen of the US, to go overseas and live an uncomfortable & deceiving life.
That is.
I lived for some years with an Argentinian girl. His father is a Spaniard emigrant in Buenos Aires. Three of his grandparents were Spaniards, one of them was an Italian.
It was no easy for her having the Spanish nationality (thought she actually got it), and if you are an illegal but you are used to develoop qualifyed jobs... well, maybe you'll have luck, but... it's hard. She left a comfortable life in Argentina (she came before the crack): she wanted to make a change, and now she did it, what it were good moments.. and hard moments too.
Leaving your country is easy when YOU'VE GOT THE MONEY. Any other way, it's a hard decision specially if you already have a comfortable life in your own country. I lived with an immigrant, and ok, she was white, blonde, she spoke Spanish with a beautiful accent, she had all the help that I could provide... but it wasn't easy for her. She didn't need to take a unqualifyed job, but it took several months for her to get her first job in the branch that she always worked in her country. She is finally quite adapted, but the nationality helped a lot: it's very important.
Look, if you were in trouble in your country or you had an adventure spirit, I'd say "go for the experience now, Spain sure is a good country to live in". But it seems to me that you are quite comfortable in the US and you don't seem to live an adventure.. anyway, it's your decision.
I don't mean that it will be a hell, but I'm tryng to advice that the first months, or even the first one or two years, it could be stressing sometimes. It depends much on what are you leaving behind, and what are you hoping to achieve, and, specially, how much soon do you want to achieve it.
And, of course, it depends very much of what are your resources (your personal resources, and the help of people that you may know in the country). And if depends of the luck a little bit.
That I've said is just my experience, and I believe it's true for any country you want to move in. Spain is my country and of course I consider it's a very good place to live. But I was born here and I didn't have to pay for a "entrance ticket". The USA are also a good place to live, but my Brother-in-law had to pay a "ticket" too in there... he's ok now in the US, but he went through very hard times and many times he was on the point of giving up and return to his country.
If you finally make it, you won't regret: just be aware of the price you could have to pay.
Anyway let me say that, If you come to Spain, you're so welcome. Good luck.