Morally right or not, even the US and allies have a limit to how many military resources exist and at what rate they can produce more. Fighting on three fronts at the same time, especially when one of them involves a country that supplies much of your industrial capacity, just isn't viable.
This is true, but there's an objectively worse middle ground (that we're in now) where the US deterrent lacks credibility so random semi-functional states are starting shit and the US drains capacity by half-heartedly responding to them (aka Houthis, Russia, Hamas, etc).
If there was a firm belief "The US will respond in force to aggression" it would prevent the attempts, and the US would stop wasting ordinance responding in a halfassed way.
Alternately, the US could just do nothing outside of the 1-2 regions it cares about (ie, the pacific). But the current status isn't great.
You underestimate the US military industrial complex.
Today it’s less an industrial complex and more a graft and lobbying complex.
Look at the amount of equipment US has lost in Vietnam - 10,000 aircraft, including strategic bombers! incomparably more ammunition. Those losses were considered sustainable!
Now it can’t produce enough dumb artillery shells!
US military doctrine doesn't _use_ dumb artillery shells, because it assumes total air superiority.
That’s a questionable assumption, but fine - look at production capacity of air to ground missiles, or whatever it is that you think is relevant.
You will find that US can only produce a fraction of what it could in 1970’s.
No further production is necessary. Simply loan out a few fully stocked Ohio-class subs and watch how quickly the bullies back off.