The thing is that having 10x the casualties tends to create more fighters.
Until it doesn’t. Case in point is that large empires exist. Greece has the 300 story, yet were part of Rome and The Ottomans. China has Tibet. US has native lands. I get your point but freedom fighters depend on sponsorship (Haiti bring an exception) and they do exhaust. Still my point is that super powers can be defeated, its just at a very high cost.