Well, there is the question of terms that end the great war.
I'd assume that the US is not involved, the UK gets off easily, and France and Italy are screwed as badly as Brest-Litovsk screwed Russia.
Austria Hungary is very fragile--and adding a large Italian Minority as well as a restive Serbian Puppet is not going to improve the situation. I'd imagine that the likely answer is that the nation splinters, requiring German intervention to manage. Austria Hungary might linger as a unstable power, or it might opt to federalize to some degree. The Ottoman Empire, perhaps more confident than Austria Hungary, survives at least one generation by massive police efforts against rebels.
Germany gets big, and becomes the dominant world power, perhaps in some state of rivalry between the UK and itself. France and Italy both want blood, although it's quite possible that these nations plunge into civil war between nationalists and socialists instead of establishing military regimes.
The world power balance is unstable, and the failing Austrian (Federalized?) state and Ottoman Empire would mean that German hegemony would be imcomplete.
This is all happening while Japan, win or lose, continues to covet China and probably has grabbed part of Russia during its traumatic civil war. The Soviets will win the conflict, but they will be forced to concede their far west and east holdings.
By the 1930s and 40s, some combination of these players will align against another set of powers. Germany and a tangled situation in Austria-Hungary will surely face France and Italy, while Japan will eventually provoke a general war against China after enough incidents.
The United Kingdom would probably look towards the United States for security, in spite of no WW1 involvement, as the USA is the best potential friend it can have. The resulting War in Europe would either be Germany + Allies vs. a Fascist Alliance or a Socialist Alliance, and with Germany's advantages in this conflict they are likely to win the rematch--possibly with nuclear weapons.
Today, the world would face a "United Europe" where Germany is the great heroes and treacherous Italians and Belligerent French are kept on a short leash. Germany, the United Kingdom and the USA informally keep the peace, while a Reborn Russia (emergent in the 1970s), Japan and some kind of Turkish successor state play in the second tier of powers.
Compared to our world where the USA stands above all, a CP dominant world would be one where empires and politics were multipolar and the threat of nuclear destruction is the chief deterrent for a third world war. The heroes and villains would change, and I suspect that the informal German-USA-UK friendship would probably lead the world.
This would mean a world where French and Japanese trade with the USA was minimal but German stuff would be everywhere. German culture, rich with legends and stories would not be suppressed under a Nazi Stigma, as Italian or French cultures would be, but would become something to celebrate.
Its impossible to truly understand what this would mean; but it would probably be a world where the ghosts of the past would continue to harry the present--in this case, rogue states and powers would still be in Europe...