The term “Judeo-Christian” was invented in the 1940’s as a response to the rise of Nazism and anti-Semitism in America.
As a historical fact, the idea that America is a Judeo-Christian nation is nonsense. In many ways, America represents a rejection of Judeo-Christian values.
At the time of the United States’ founding, the vast majority of Christians and Jews lived in outside America – and they held very different moral values than Americans. Everything that defines America – the belief in the inalienable rights of the individual, the importance of property rights and free markets, equality before the law, and the separation of religion and state was unheard of in both Christendom, and the pre-modern Jewish communities. The United States were formed as a rejection of both incessant religious conflict and economic meddling in the European kingdoms.
The ironic reason that most Americans today believe that Judeo-Christian values represent some kind of universal Western ideal is that Americans (inspired by European philosophers) exported anti-Christian enlightenment liberalism to the rest of the world, and converted Christians, Jews, and everyone else to their worldview.