It depends what era of Earth we're talking about.
Present day Earth wouldn't stand a chance against the Industialists of Oddworld (since the natives are a peaceful folk). Oddworld has a larger supply of armour, weapons, and man power than Earth, since it's 10x larger. Also, they're ahead in technology (chant orbs that hover, electrial devises that can turn a foe into dust, etc.) so there's little hope for Earth unless they agree to help them wipe out the natives.
Now if we're talking future earth as in ages (like millenia) from now...

The Imperium of man has concured thousands of planets with their elite soldiers, the Space Marines, and are certainly not going to back down from these bunch of aliens.
