Natural US citizen, becoming dual national in Europe?

[paredesheranz 0]

I realize this is an old thread, but I have been scouring the internet for some answers, and the original post here resembles my situation...I'm hoping someone may still read this...

I am a US Citizen-born in US to Spanish mom. My Cuban father did not become a Spanish Citizen, but was fullly entitled to citizenship, as both his parents were nationals, he married a Spaniard and lived there for 10 years.

I am now applying to Spanish citizenship as I may be moving to Europe in the coming years. I understand that to receive Spanish citizenship, I must renouce my American one in the eyes of Spain, but the US does not recognize an oath I make renouncing citizenship in front of a Spanish magistrate and that in the eyes of the US I will continue to be a US citizen unless I sign an oath in a US consulate in a foreign country. Can anyone confirm what type of renunciation Spain requires? Also, when traveling between the US and Spain, can/should I enter Spain with my American passport or my Spanish one? If I have supposedly renounced my American citizenship, how would it be seen if I enter Spain with an American passport? I ask because I am first and foremost American and do not want to jeopardize breaking any American laws by entering a foreign country with another passport, if there are any laws of this kind. Or does one only need to exit and enter the US with an American passport?

Thanks in advance for any reponse that may help. It seems that there is a lot of conflicting/subjective information out there so I am hoping to find someone that has traveled with a situation similar to mine. Thanks again!!