I see where your thinking comes from but your missing the next step. It goes like this...
100 x US bots
100 x China bots
Guy A - " wow look at them go, this is great like robot wars for real"
Guy B -"yea, so much better than real fighting where people get killed"
Guy A - "Huh, true... but, why are we fighting"
Guy B - "Remember that last carrot on earth we all needed now that we used all of earth resources to build weapons"
Guy A - "Ahhhh yes...."
Fight rages on ....
"Results just in, China 90 bots destroyed..."
Guy A & Guy B "YAY we did it, yaaaaay"
"America 100 bots destroyed"
THE LAST 10 CHINA BOTS KILL EVERYONE
War happens for a reason, a purpose. Fighting is not linear. If you lose your defence bots you will still have to fight with real people and perhaps given an army of robots capabilities many thousands of armed men..