The My Little Pony Movie was amazing, with wonderful world building and well plotted out adventure and feels. But it ignored a lot of canon. Twilight has check lists for checking her check lists! Do you really think she wouldn't have a plan for an invasion, especially after what happened at Cadence's wedding? Also, Equestria already has friends and allies they could call on. So, here's my version of events.
Edit: Some of the early comments have given me cause to think about revising the second chapter, so I'm pulling it until I have a chance to do so. I may remove it altogether and let the first chapter stand on it's own, as I originally intended. The idea, after all, was to show that Equestria already had allies they could have called on, not to mock the actual film, which I enjoyed thoroughly.