The kingdom of God is not and has never been in anywhere in the United States of America. Not in anywhere in Israel, Italy, Asia or Africa and can never be. The kingdom of God starts in the hearts of believers in Christ. Whereever the king is that's where his kingdom is situated. However, the literal kingdom of God will be made manifest to the citizens of the kingdom when the enemies of God are put under the feet of his son Jesus Christ.
Revelation 21:21 describes the physical features of this kingdom. This cannot be a city made by man.