How well could all life on Earth, working together, defend the planet?

Hypothetically—

Think Avatar-esque. When the humans and the na’avi went into war, all the species of Pandora wound up being able to defeat the machinery with their own natural capacities.

So if we had an alien species coming in to do whatever with our planet and they wanted us out of the way… sidestepping the how for a moment, if all creatures on Earth were of the same mindset to launch an attack on the invaders, how would we fare?
(Because I’m thinking our weapons would seem like bows and arrows to aliens coming to our planet… who knows what technology the aliens would have…)

Do you think us earthly beings have what it takes?