I created a blog with all post in english and spanish, but google indexed it as spanish page. I'm investigating the cause.
Does google see the language that I use in google webmaster tools page when I sent my sitemap?
Does google see the country of owner of the domain in whois? In the whois of the domain the country is spain.

That is pretty interesting. I have never encountered that before. Your guess is as good as mine. They could be looking at the WHOIS or considering the density of Spanish words on the page, Google might be assuming your audience would be Spanish speaking visitors and classified you as such.
Let me ask you, is this a problem for you? Who is your audience?
I wonder if these tags would influence Google any differently?
code: <META HTTP-EQUIV="Content-Language" CONTENT="EN">
<META NAME="distribution" CONTENT="Global">

Those meta tags do nothing for Google or for any major search engine.