Possible Move from the US, Looking to Learn

Hello Everyone, Apologies in advance if this post breaks any of the rules of the subreddit, please let me know if changes need to be made. I'll start with some context before asking my questions: I'm an Italian citizen (29M) that came to live to the U.S when I was around 15, because of my parent's work. Fast forwarding to about 2 years ago, when I started working as a Software Dev and started putting money in the stock market and my 401k here in the US (I'm not sure what the equivalent is in EU)