You need to work with a family law attorney in your area. More facts are needed. However, please bear in mind that even if there may be the possibility (or not) that you may be adopted under California law, your parents may have also some recourse under Italian law. My suggestion is also to consult with a family law attorney in Italy. Good luck.
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You may have problems with terminating your parents' rights. But, even if you succeed, if you are hoping to get US citizenship, that won't happen because you are over 16 years old. Good luck!
This really does not sound very practical. You will need to consult with an attorney and explain the intent of the adoption and the full circumstances why you consider this a good plan for you.
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