The official novelization mentions conventional assets against kaiju, actually. The first kaiju takes three distinct strikes to take down, and the area made totally uninhabitable by its remains encompasses most of the San Francisco area, with zones of contamination stretching much farther. The site is also, for some reason, the jaeger graveyard.
Specifically mentioned are tanks and their cannons, which do **** all, and Hellfire missiles, which are mentioned as being able to "hurt", but unable to take one down.
Granted, I doubt the author was quite the authority on state of the art first-world militaries, but it still seems rather more wasteful to send an entire army group that won't be able to do all that much at all against a monster that can much more effectively (and much more badass-edly) be demolished with a giant robot.