Well France is at 1.8% and are actively involved in terror operations in countries very few dare go, this includes the FFL operating in Africa with some great successes. They have state interests there so they operate as they must and they quietly go it alone and deal with a number of outside threats.
As it were, I don't think France is shy to get involved in activities where their interests lie. The issue here is finding common ground; of which fighting terror is clearly an issue they share. France certainly should get over the 2% hump, as they and all other NATO nations agreed to.
The video itself isn't a smirk, but more of a shared reaction from others who probably speak French it would seem. Notice the one leader with the hand on his face, leaning over and chatting under his breath? Appears they were having a conversation about the lecture they were receiving.
Besides, when you are getting scolded like a student in the principles office; rightfully so in some respects, you are bound to have one of those looks. I recall George W Bush at Trumps inauguration with a big smile on his face as Trump let loose on the poor decisions of past politicians and how things were going to change. I think it's just so rare to find a politician be more of a football coach than an entitled, carefully crafted patsy, that people just smile or react differently.
I can't lie I had a big laugh listening to Trump also because I could see he wasn't going to let the under funding from NATO go. How can I not root him on when he is transparently calling out the abuses and exploitation of America? He's like a dog on a bone and these politicians clearly expected a more gentle, diplomatic response.
As Trump would say. "Wrong!"