Stopping an initial infestation would be easier than if dinosaurs were suddenly everywhere. People have too much faith in technology. We've had a rampant cannabis growing problem in Kentucky since twenty years before I was born because people can't see below the canopies of the deciduous forest. If they can't stop weed from growing how they gonna stop dinosaurs from trekking around under cover? Maybe big rexes but man sized raptors?
Also people always never consider politics in this scenario. Your country isn't going to want to lob around artillery on its home turf. And no one is going to want to throw around artillery on a friendlies turf either. And just because first world countries have advanced imaging techniques doesn't mean a third world country is going to want you to come in anyways.
Dudes with AKs, cell phones, and artillery shells have drawn out the conflict with the most technologically efficient coalition in history for a variety of reasons. Never underestimate any opponent.
