Taxes in US vs Spain

[Work in progress]

Top level, I want to compare couple of countries (US vs Spain) which could be considered quite different from social policies, one often cited as extreme capitalism and the other more of socialist nature (who likes to talk about "el estado del bienestar"). I am not an economist or have experience creating a company so I may miss stuff, but let me give it a try. We would like to learn:

1. If you make a given salary, how much you get to keep, depending on the place.
2. And related, what do you get for what you pay on your taxes. Or a bit on the flip side. If you have certain needs in life you have to pay for and the rest of the money you get to keep to enjoy, where is better (assuming you were making the same, which obviously may not be the case).
3. If you are a company, where is cheaper to hire someone. This is more from the perspective of where would you like to invest. Of course, there are other factors, like how easy is to pull out if things go bad (like the cost of laying off people, etc) or what are the corporate taxes...

So, with we dig in both countries and try to make a comparison, which obviously may not be easy. This will be even more difficult if we try to cover a broad spectrum (low and high income, etc). So, we may just want to pick an example. 

I'll put here the summary table once I get it all. For the time being few posts getting the background info:

1. How much is to hire someone in Spain?
2. Income tax brackets in Spain
3. Income tax brackets in US
4. Paying taxes in Spain (II): taxes on your wealth.

Cheers!