Defeated nations are easy to deal with; in this era where might makes right, if they don't submit, just fight another battle.
Without Britannia leading the charge, Japan and the United States, even if they wanted to make trouble, wouldn't be able to create any substantial impact.
What really requires the Vienna Government's attention is the once good ally—Russian Empire.
Times have changed. With the victory of the world war, the dragon slayers have replaced the role of the evil dragons.
Identities have shifted, and naturally, so have stances. Former allies have now become competitors.
Whether or not to strike a fatal blow to the Russian Empire while it's down is a topic worth studying.
The Russian civil war has already reached its climax, with the rebel army's momentum growing by the day, bolstered by the unwavering support of European nations, sweeping through much of the Russian Empire.