We needed France.
Charles Carroll was from Maryland, which had been very tolerant of Catholics.
About France: We benefitted greatly from the propensity of France to tick off Britain.
Actually, I don’t think it was that cynical (for one thing, the French had been heavily, if not officially, on the side of the Protestants for a long time). The Founders realized that a state church wasn’t a good idea and even though the Anglicans didn’t like the Congregationalists and vice versa, and nobody liked the Catholics, they understood that the Judeo Christian nucleus had to be the foundation of this new country.