The United States should remove both "Under God" and "In God we trust" from both the Pledge of Allegiance as well as all US Currency, because:
1. The United States was founded on principles of individual liberty, not Christianity.
2. People who do not identify as or affiliate with Christianity can be loyal to the United States without accepting the Christian religion, and as such should not be required to express Christian beliefs when pledging said loyalty.
3. "Under God" was added to the Pledge only in 1954, as a response to fear of communism, which in today's world is no longer a major threat.
4. "Congress shall make no law respecting an establishment of religion..." The 1st Amendment states EXPLICITLY that Congress will not recognize a religious establishment.