Try this
America enters the civil war as IOTL but the Trent incident is allowed to get out of hand and the CSA gets a reluctant ally which contents itself with a naval blockade and supplying the midwest indian tribes with up to date weaponry .This results in a stalemate where neither side is able overcome the other and both are unable to gather enough strengh to expand westwards.There will be peace eventually, but Lincoln was right the divided house falls and any impetus is lost in rebuilding. Maybe we end up with a truncated USA, a CSA ,a union of western states and just possibly a federation of the midwest indian tribes.
So no transcontinental railways, no expansion, reduced immigration due to reduced economies and political/racial unrest etc
UK
Takes a more active role in emmigration begining with the removal of a large proportion of Irelands population in the 1840's..Something like 2,000,000 people are moved to Africa,Canada, Australia and N.Z. This could arrise from alarm at the rising population and a greater wish to 'make the world England' maybe a super empire league with a political voice could sponser 'Ten pound poms' a hundred years early.
All those emmigrants need British manufactured goods which means more manfacturing which means more investment, which means more research, more discoveries etc etc etc
Some earlier than OTL education reform acts would not hurt either.
So we have a stonger empire with people less unevenly distrubuted, a more inovative UK with maybe some earlier moves to empire federation
Russia
Not looking forward to this one
but here goes
we need a new Peter the Great on steroids with a long life ,as before he dies he needs to free the serfs early in the ninteenth century, educate them and give them some form of political life.Next he needs to open up Russia to ideas ie no reactionary censorship and encourage people to enter Russia on a massive scale ,and build up the economy quickly as he will need new money to stabilise the country as every boyar from Minsk to Vladivostock will be against these reforms. somehow he is going to have to get the majority of the guys 'on board'
So by 1900 we have Russia maybe looking semi modern
Germany pretty much as IOTL Prussian dominated federation with rising population growing economy and starting to annoy the UK
WW1 can start any time after 1908 and will eventually though not at the start involve the UK and Russia [they can come in at different times though and both against the CP ] British naval force and Russian manpower overcome German military genius and a peace is declared which just as IOTL leads to 'a' WW2 which leads to a triumphant UK and Russia staring at each other over the soon to be dismembered corpse of Germany
This has so many PODS
If I was clever I would be able to think of just one