"USA does NOT do this alone, contrary to what you seem to imply"

It's not even debatable that the U.S. is NATO. It is. There is no NATO without the U.S.

Canada "going in where needed" is what it's supposed to do. It has nothing to do with a special excuse for Canada not to pay 2%.
By being the biggest laggard in NATO you get to send a grand total of 6 jet fighters to Syria and your excuse, literally and I kid you not, is that you have a small military and that's all you can send.

Being an adult I can tell you there is nothing you can say that allows you to weasel out of not paying for your defense.