Renouncing your US citizenship is not that easy, especially if the US gov't belives you are doing so for tax purposes.
US gov't
"Also, persons who wish to renounce U.S. citizenship should also be aware that the fact that a person has renounced U.S. citizenship may have no effect whatsoever on his or her U.S. tax or military service obligations (contact the Internal Revenue Service or U.S. Selective Service for more information)."