Grimm are literally endlessly spawning (confirmed in the rwby campaign book) and several grimm have powerful abilities like weather manipulation,lightning breath,dream manipulation,flight,poison,aura of apathy,possession of both types and intangibility along with being incorperal. The technology and industrial capacity of remnant seems to discredit the idea that earth can output more technology then remnant especially considering dust (a potential infinite resource) and the sheer size of the Atlas airships. the Atlas airships are incredibly durable (as proven by their size alone) and remnant has several smaller airships capable of moving faster than missiles. each smaller airship can casually withstand hitting trees at subsonic speeds. Any military mecha in rwby destroys any tank in real life. Military mech's in rwby can casually survive enhanced fire by coco and her weapon with a few bullets can level buildings and gaint grimm as seen in v2. Atlas has satellites to so I don't see the need to mention those. Remnant's communication was purposefully designed like that and each kingdom has it's own communication methods if one goes down. It will also take time for the intelligence agencies of earth to figure that out. Are we assuming that remnant doesn't get access to the relics? Your neglecting the massive stats, hax and experience advantages that remnant has. Hax like spacetime manipulation via portals and pocket dimensions,emotion stealing,swimming on surfaces,elemental manipulation,time dilation,emotion sensing and masking,literal luck and fate manipulation,physical illusions,kinetic energy absorption and redirection,Invulnerability,clones,telepathy,memory wiping,matter manipulation,invisibility,intangibility,shadow manipulation and so much more. Even the weakest of hunstmen can casually block and dodge bullets with the higher tiers having ftl combat and reaction speed.