Franz Ferdinand may disagree!
Lol there are about a hundred things that could kick off WW III, but I doubt a politician from a small country which the average joe barely realizes even exists getting shot by some senile nutcase is one of those things.
The difference is that Austria-Hungary (as unbelievable as it may sound nowadays) was actually considered a great power in Europe before WWI kicked off. And Franz Ferdinand was the heir to the throne back in a time when a nation and being a heir to a throne actually meant something.
That's not the same situation as a politician from a country nobody truly gives a shit about getting shot in a time where deep down not a single person in Europe truly gives a solitary fuck about some politician.