Why do you think Austria made the ultimatum so difficult for
Serbia to accept?

On receipt of the ultimatum, Serbia at once appealed to Russia, whose council of ministers met on July 24 to determine a course of action. Russian Foreign Minister Sergey Sazonov voiced his belief that Germany was using the crisis over the archduke’s death as a pretext for starting a preventive war to defend its interests in the region. Defying Austro-German expectations that Russia would back down in the case of such a conflict, the council agreed to order four military districts to prepare for mobilization.

Learn more on: https://www.history.com/this-day-in-history/austria-hungary-issues-ultimatum-to-serbia

i would say that the politicial parties from state to state varies.