Pondering move from U.S to London or Spain

I know this topic has probably come up a bunch of times. I am a 21 year old male from New Jersey, a recent college graduate with a degree in finance. I have wanted to move out of the country for many years for numerous reasons. Mainly because I think being a business major having international experience would only benefit me and my career. My options are currently London or a large city in Spain. My girlfriend is really excited about my decision to move out of the country and she can't wait to move with me. She is the type that will just do something on the spot, were I am the opposite and I think about things and research everything. She also speaks 3 languages: Spanish, German, and some Italian. Were I speak just English.

My questions are:

How hard would it be for an American, with a degree, to obtain a job in London in Spain?

If I wanted to continue my degree how hard would it be for an American to get into a graduate school?

With currency conversions, how much money should be brought to live on, and what is the standard of living comparative to living in New York City?

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I'm so excited to do this, some days I just want to pack my bags and leave. However, I am still a little scared because of the extremely sheltered lives Americans live. That’s another reason why I want to leave. I'm young and want to experience other cultures before I have obligations that do not allow me to. My family is not fond of the idea of me living because they have never been there and they have no idea what to expect. They keep feeding me this negative propaganda shit that has no relevance to me. If I could I would like to get in contact with other Americans who have moved and how they like living outside the states.

Thanks in advance for all your advice!!

-Darion