The point that you seem to obviously have missed is that France stuck it's neck in the noose with ours with only a hope of future trade as any possible reward. They weren't hoping for hand-outs down the road and their goose would have been cooked right along with ours had we lost. Capish?
And it had nothing to do with France's enemy named England, who they'd been fighting for centuries?
Actually France supporting us was more analogous to us supporting the Mujahadeen. Their enemy was our enemy.