The Continental War of 1914-1916 reoriented Europe and established Germany and Austria as the preeminent powers.
France was defeated and force to cede Belfort, Briey-Longwy, and all of Lorraine east of the Moselle River to Germany.
In the east, Russia was forced to cede Congress Poland, Lithuania, Courland, Kars, Batumi, and Yerevan.
Serbia was vassalized, Montenegro annexed, Bulgaria expanded, and Austria satisfied.
It was messy, but the social cost was relatively limited compare to, say, the upheavals of 1848 or the Napoleonic Wars.
What if the war had been more drawn out and socially disruptive?
For one, it's entirely possible that the Great War might not have been as massively damaging, or as horrific as it was-the Ottoman Empire and Austria-Hungary in particular never fully recovered from the conflict, and anti-German sentiment remained a
huge problem in France
and Italy until the early 1960s, mainly thanks to the devastation wreaked upon both countries. Also, probably no 2nd Mexican War, either(and so, Baja California, Sonora and Chihuahua never become states in 1957, which may also mean that Alaska and Hawa'ii may not be admitted in 1947 as IOTL, depending on butterflies)
The Ottomans certainly did quite fine when they struck oil
For a while, things arguably were looking truly positive for them, yes, from about 1917 to 1933 when the war broke out-but after that, even oil couldn't stop them from falling apart in the late '70s(and the tragedies that followed in the '80s, much like after A-H's collapse in 1946-though arguably, at least the Danubian Federation has largely gotten over it's predecessor's failures since it's formation in 1972).
OOC: Think of the Balkan Wars of OTL, only writ large. (And, sadly, it's doubtful A-H would have been able to survive in it's then original form to the present, with such a late POD, as it had too many problems to overcome-hope glenn67 doesn't mind too much!)
Why are people assuming that the USA would go to war against Germany? They were plenty salty about what happened in Venezuela in 1895, and to this day large portions of the US population are Germanophone. No way they can go to war with Britain without massive backlash from the Socialists, Irish, and Germans, which would cause major political unrest. Even if you did, it seems more likely for the USA to get involved against Britain for freedom of the seas violations, if only because Britain would have more supremacy over the seas.
Interesting possibility here(though we allied with Germany only after the Ottomans declared war on us over the Harriman Telegram incident, so named for the current American ambassador to the Ottomans at the time), though I should point out that there actually aren't very many fluent (non-Amish) German speakers around today outside of some parts of Wisconsin and Texas, maybe 200,000 at most, and most of them 60 or older.
Someone should also use our conclusions to make a mäp comparing a longer-war scenario to OTL
James Turtledove's classic trilogy from back in the '90s, anyone? Here's
a link to the official fan site, if anyone's interested.