Really? That's the immersion breaker? Not the fact that they are cat girls in Normandy invasion?
Someone browsing War is Hell pool #14484 probably isn't expecting a meme, and to date this is the only post tagged as such. Did we really have to hound him and pretend he's moronic for presumably not noticing cat ears? Catgirls alone might not be particularly thought-provoking to those accustomed to anime culture and may fall under suspension of disbelief.
Immersive doesn't necessarily mean realistic, though an unrealistic element may break immersion by making the audience point and laugh/complain at its ridiculousness. Breaking immersion "pulls you out of it", like (maybe too literal) if you are dreaming in your sleep and a loud alarm clock wakes you up. In this case, someone was distracted by the soyjack pointing throwing off the tone aside from the fact the artist did it on purpose (which he might not have known).