The burden of proof falls on the person making the chiddush. You know that every major posek does not hold of a chiyuv to join the IDF and actively discourages it. Why don’t you bring a proof of someone who DOES hold of your milchemes chova idea? As far as I can tell, it’s one individual CR user bringing proofs from tanach versus every mainstream rabbi.
The proof that they don’t hold by your theory is evident in the fact that they discourage joining the IDF. So, instead of asking us to find places where they specifically address your weird, new defense for drafting Chareidim, why don’t you supply one actual person who agrees with you.
Your scrambling to preserve your intellectual honesty by claiming we would theoretically have a chiyuv to join the American army proves the weakness of your stance. How much more could I get you do admit in your quest for consistency? Would we have a chiyuv to serve in the Czar’s army if Russia needed defense? Would we have a chiyuv to serve in Mussolini’s army if he needed soldiers? You have completely invented this idea that Jews are halchically bound to join the army of whatever country they happen to be residing in. It’s just not true, and nobody before you has ever claimed it is.