“the French draining their treasury”. Yep, but not only that. I think that Louis the XVI saw it as a great opportunity to regain what Louis the XV lost. Because not only the French was providing money and troops (l'expedition particuliere) to the US rebels, but also regained all the part of India they’ve lost before. The French Fleet was attacking the British fleet and won two major tactical battles, allowing the re-conquest of some towns in India.

Because the Americans signed a separated peace (against previous agreement) the King had no choice to give back his gain to the English, and couldn’t take back Canada and all the lost territories. He was left just wit a HUGE debt, no possibility of trade and upset English.