Update: Seems definitely not possible to get tax deduction in France for an American organisation.
This post from Don Efficace, the organisation which was trying to set up EA regranting in France, explains what are the constraints for the French tax deduction: https://forum.effectivealtruism.org/posts/jWhFmavJ9cE2zE585/procedure-to-allow-donations-to-european-organizations-to-be
Update: Seems definitely not possible to get tax deduction in France for an American organisation.
This post from Don Efficace, the organisation which was trying to set up EA regranting in France, explains what are the constraints for the French tax deduction: https://forum.effectivealtruism.org/posts/jWhFmavJ9cE2zE585/procedure-to-allow-donations-to-european-organizations-to-be