I've seen this done as a backdrop or as a backstory to several fics. Basically Voldemort is too heavy handed and the SoS is beginning to fall apart, so the International Confederation of Wizards (or some other organisation) performs either a UN style intervention or picks a side (usually the anti-Voldemort side).

So some questions:

• What does it take to get them to intervene? In canon they had giants wandering around some city killing people and destroying stuff. Is something like this big enough to get them to consider intervening? I presume the MoM can magic away all muggle memories, photos, footage etc, but they are limited by manpower. If they don't have enough people and/or the event is too big then the event gets picked up by the news and it gets even more difficult to contain.
• If it does get to the point of intervention is their intent just to stop SoS violations or will they go full on change of government intervention? If their only concern is stopping SoS violations they might just decide to negotiate with the Voldemort regime and ask him to tone it down.
• If they go full intervention, what do they do? Send a small number of volunteer troops, send supplies, or maybe total war? It's difficult to tell what large-scale warfare looks like in the magical world. The Battle for Hogwarts is really our only reference (almost everything else in the story was asymmetric warfare) and that was static warfare with a smaller (?) force holding out against a larger one, not something far more mobile like you would find in peer opponents.

Ideas? I'm thinking about a larger wizarding war story.

 

Honestly, I think it's incredibly difficult to break the SOS. The majority of the Ministry's existence is to hide magic from muggles. That's their prime purpose. I mean, in the context of canon, the Ministry is rarely shown in a competent light, but even so, you'd think it would be pretty easy to miss a witness just once. So then part of the burden lies on the muggle side of things. Even if a muggles does see something, and happened to not get obliviated, whose going to believe them? And what are they going to believe what they saw? There are muggles who are willing to believe magic is real. But then there are muggles who will always come up with a rationalization or an excuse for what they saw. And, time has the effect of blurring memories. Perhaps what they think they saw isn't actually what they saw. They're left with simple supernatural drinking stories to share with their buddies.

All I'm saying is that it would take something drastic to break the SOS. Perhaps the invention of cellphone cameras will be the nail in the coffin, or maybe just widespread use of the internet. But there's already imaging satellites flying over the entire planet in the 90s. Once technology gets better, it's even easier to say something is spoofed. I think it would have to be an intentional act to break the SoS. Like something from a superhero movie like Voldemort hijacking every tv set across the entire world and declaring that magic is real and then remotely setting every tv in the world on fire.

 

Yeah, I suspect if someone caught real HP magic in action and uploaded it to YouTube the response would be dozens of comments along the lines of "This looks fake as shit" and "I could do better effects than this in half an hour."