Q: "Well if the Jews managed to gain control over all of these countries and made them indebted and slaves to their agenda, then what difference do those extra 30 IQ points really even make? If the Jews were already able to take control and push their agenda before mass immigration?"
A: Let's depersonalize your question a little by replacing the term "Jews", which might be construed as "antisemitic", with the variable Z (which might stand for any group or combination of groups whatsoever). That way, we can avoid pinning everything on one homogeneous group of scapegoats.
You seem to mean something like this:
"If Z is really smart enough to have used us up fighting their battles and already killed half of us off, then really, aren't we White people already so stupid that it's irrelevant if we lose on average 30 IQ points by indiscriminate miscegenation (the forcible Africanization of Europe and North America via "le metissage")? Stupid is stupid, right? Isn't it true that Z deserves to inherit the Earth because they're smarter?"
Not really. This would amount to conflating trust with stupidity, which would be very stupid indeed. The US, much like the older White Christian societies of Europe, was explicitly designed to be a "high trust society" reflecting the noble ideas of European philosophy enshrined in its Constitution. The idea was to honor the best in man and cultivate the noblest aspects of human nature. Unfortunately, our trust was systematically betrayed by the liars, cheats, and thieves of Z. Trying to see the best in people, we acted in good faith and befriended secret enemies who plotted our destruction and infiltrated our political-economic system by falsely promising their loyalty.
Use your common sense. Many intelligent people have been swindled and ruined because they charitably granted the benefit of the doubt to far less intelligent but amoral grifters, just as many strong people, believing themselves engaged in fair competition, have been poisoned at dinner, stabbed in the back, assassinated in their sleep, and conveniently eliminated in fake "accidents" born of malevolent conspiracies.
Obviously, White people - who built modern civilization almost single-handedly - are not "stupid". Calling the victims of treachery "stupid" reduces intelligence to sheer evil.
That in itself would be evil.