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I'm working on a scenario that's a bit too complicated to go into, but I can't seem to get a handle on one aspect of it:

In the scenario Sicilian troops end up invading the Papal States and killing the Pope in 1854 (the POD is more than a hundred years prior in case you're wondering why the Papal States still exist or why Sicilians are invading them).

My question is this: what kind of reaction would this cause? How upset would Catholics be over this? Would nations choose to go to war over the matter? I'm trying to gauge a reasonable reaction.
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