It was called "Warstrider", by Ian Douglas! I clearly remember the cover having the word "Xenophobe", big and bold, on the cover, though, along with a huge black/silver alien thing looking like the creatures from Pitch Black, bearing down on a guy.
Humans had nanotech films on their brains for interfacing with computer systems, eastern culture had become dominant, the aliens used Silver Surfer-looking nanotech mechs that split into smaller mechs once defeated and at some point, humans came into contact with a third alien race using biotech that also wanted to help defeat the antagonist aliens. The ending had a twist about the true nature of the attacking race.
The reference to crunchies is when Corporal Castellano tells the main protagonist Dev:
"The poor bloody infantry, sonny. Crunchies, the striderjacks call 'em,'cause that's the sound they make when their CAs get stepped on by the big five-meter jobs."
