Hi everybody.
I am a U.S. citizen and have been legally working in Spain for 5 years. I was recently granted my 5 year residency permit (el permiso de residencia de larga duración), so in 2017 I will have legally lived and worked in Spain for a total of 10 years and be eligible to obtain Spanish citizenship. It would be nice to be a Spanish citizen, as I would like to not have to worry about things like autorizaciones de regresos and making sure I do not stay out of the country too long, jeopardizing my chances to renew the work permit. I have already started to look into the process and honestly it seems pretty straightforward except for the fact that Spain does not allow dual citizenship with the United States. From what I gather looking on the web, if I were to obtain Spanish citizenship, I would have to declare before the Spanish authorities that I renounce my U.S. citizenship. As a result, Spain would no longer recognize me as a U.S. citizen. However, the U.S. would still recognize me as a U.S. citizen, since the only way to renounce my citizenship (besides doing something extreme like joining a foreign army which is at war with the U.S.

) is to go the U.S embassy and formally renounce my citizenship.
Are there any Americans out there who have gone through this experience? Do you have any advice? Does anyone know what kind of proof the Spanish government would need that I had renounced my U.S. citizenship? Although I would like to have a Spanish passport with all the advantages that come along with it, I certainly would not want to give up my U.S. citizenship.
Thanks in advance for any advice anyone can give me.