I think the poster wished for more detail on how Germany won WW1 (specific battles, campaigns, etc), not why. As you say, combine the US and Germany and the alliance is pretty hard to beat. One of my biggest frustrations of TL-191 is the fact that we learn so little about the global war going on except through the awful "You know Sam, I read the other day that Germany...." technique.
I think the gap has to be filled by US (us not the United States)
Basically you can assume that - initially - a CS victory will not change much for Europe
Prussia will fight Austria for the hegemony in Germany
After that a Franco Prussian war is most likely, so until the onset of How Few Remain in Europe virtaally nothing will have changed.
The Scramble for Africa and Asia will also be not really different as both CSA and US will still be occupied in America (here you get changes Cuba is bought, no Panama canal (IIRC))
The most important change is the fact that the US is not expanding in the Pacific - its Japan that fights spain - which is beaten and teh Phillies become a Japanese posession.
Its also likely that at some point there is a Russian/Japanese war as both nations will be interested in China.
Spain probably sells its remaining posessions to Germany.
Basically you can come to the same power distribution as OTL without leaving the "path of plausibility"
Well - now to the "Great War"
THE assassination of FF - lets say this is a plot device and take it as it si (IIRC Turtledove gets him killed by a bomb - OTL it was a gunshot, so there is a difference - however a small one
)
The war starts as OTL (SchliefFen Plan, Austrian blunders, Russia defeated at Tannenberg, OE joining the CP)
You can assume that the non American theaters are just going as OTL
a few differences. Teh "ostasiengeschade" of Graf Spee (the man not the ship) is sailing to Chile and stays there as Chile is friendly to the CPs - so battle of Coronel, but no Battle of the Falklands.
IIRC Brasil joined late, so we can further disregard South America.
The biggest change is that Italy stays neutral - which will result in a better performace of Austria Hungary.
To balance I assume that UK manages to get more troops from india (offering them dominion status - did not OTL as it was not necessary - basically indian war contribution is higher to counter the absent of US loans and materials)
Overall the Entente troops are less supplied as otl, but OTL Germany and Austria fought despite low supplies, so not totally unrealistic)
So you get just the same outcome in Europe until early 1917 when russia collapses - soon afterwards the Entente sues for peace - not totally ASB.
THE naval actions I justify with a higher Japanese involvement babancing out the US navy (weaker than otl due to US/CS split of forces). THE Hochseeflotte is stronger, but the ships need recoaling possibilities to fight across an ocean - so while US navy and HSF cooperate the RN is still able to hold the lines
