Does Spain have some special work visa provision for citizens of its former colonies? Otherwise, unless you also have an EU passport, your biggest problem is that you not only have to find a job, but you have to find an employer who is willing to vouch that they are not able to hire anyone in the EU (not just Spain) to fill the position.

I think your best bet is to find work with a big accounting firm that has offices there, and tell them you would like, eventually, to be assigned there.

Your other option is to look for a company that needs an American accountant for some reason, but with no experience, your chances of finding such a job are probably slim. To get some experience in international accounting, you could look for work with some American companies with operations in Mexico. From what Stravinsky has posted, that would give you something to sell.