We follow the Lord Jesus Christ who grafted us into the tree of Israel. Who do you follow, John Appleseed?
America is not, nor was it ever a Christian nation. This was clearly established in the early 1800's by the Barbary Declaration. In order to trade with Islamic pirates (terrorists???), America decided to state unequivicolly that she was a secular state.
To try to apply promises made to Israel to the church? Thats a misapplication of Romans 11. The church wasnt given Canaan, so to say that we are in danger of loosing that inheritance is at best a stretch. (Of course, apostasy does lead to a loss of aspects of our spiritual inheritence. When a believer falls into sin and apostasy, he looses much of his communion with God until he repents. So there is an added spiritual application to the sole interpretation.