honestly, even without the typical story progression making it unlikely for the MC to fail, i feel like this situation is bad on many levels for those USNA and Soviet Union folks.
the magic association might be forced to contact the ten master clans, but while juumonji and mayumi might have just been concerned before, i could see them easily be convinced the new pressure just confirming the suggestions tastuya told them at their duel before.
so the presentation, covered potentially by the ten masters clan, as well as pixie, and of course even our very powerful friends of the mc, are quite a wall to get past by. and since those friends cover many types of magical topics, they can easily figure out an intruder or two.
then, we obviously have our MC who was just recently unsealed, which also strengthened FMC as well. you can't expect us to see them fail now anyways, anymore.
lastly, when the attempt does fail, erika will likely gladly jump in with her police connection to reveal the USNA being involved. political pressure will rise, the magic association will confirm them being pressured, and the card house might collapse. and against that tuber bomber (whatever) thing, well, unsealed tatsuya would likely be able to make it vanish before it even happens.
so, yes, i cannot see this turning out bad for our MC one way or another. lol