A move to another country is a very significant life decision. A “Green Card” is actually a “permanent resident” immigrant visa. A U.S. “permanent resident” visa comes with significant opportunities and significant responsibilities.
Permanent resident visa for immigration purposes: The visa is valid for immigration purposes only as long as the person retains the subjective intent to live permanently in the United States.
Permanent resident visa for tax purposes: Under United States law, one’s status for immigration purposes is different from one’s status for tax purposes. Generally the rules for “tax residence” are found in Internal Revenue Code Sec. 7701(b).
What follows is my answer on Quora that considers the “benefits and burdens” of the Green Card. I suggest that you read all answers to this question.
Read John Richardson's answer to What are the benefits of getting a "green card"? How has your life changed after being a green card holder? on Quora
But, wait! There’s more. If you have the Green Card for 8 years or more, you can’t leave the United States without being subject to the S. 877A Exit Taxes.
Read John Richardson's answer to Must one pay U.S. exit tax on foreign assets? on Quora