It seems to be pretty well documented the effect of WWI and II on Germany, however, how might England and France be different today if they had not lost so many lives or suffered the effects of war. Is it possible the root causes of these wars would still be smoldering today waiting to burst into flame if they had not been dealt with in the 20th century?
Just going for the UK:
The distraction of WWI made Irish Home Rule a low priority. This led to the Irish War of Independence and the secession of Ireland in 1922.
The role of women in WWI led to them getting to vote.
In the Dominions of Canada, Australia, and New Zealand a national identity emerged, and they would be granted full independence about 10 years later. This marked the beginning of the transition between Empire to Commonwealth.
The war cost the UK more than any other allied nation. Of every penny spent, 1/3 came from the UK. The national debt went up 10x. Nearly one million men died.
The UK was given several colonies by the League of Nations. Britain did not want them because they were unprofitable and cause further strain on the country.
To reconcile this, the British took a greatly reduced role for the military cutting spending hugely, under the assumption there wouldn't be another general war in Europe.
All these effects made Britain rapidly lose ground in terms of their economic stranglehold on the world. In the formal empire, 1/4 of the world depended on the UK. In the informal empire where the British had hegemony encompassed another 1/10 or so of the world. Their trade represented nearly 1/3 of the worlds trade. This was all lost because of the war.
WWII was even worse economically. In the years leading up to WWII the UK was spending money on social reform and was haemorrhaging money on the colonies that were dumped on them.
There were troubles in the colonies too from nationalist movements, particularly the Indian Empire.
All the money spent on rearmament was basically thrown away as the BEF was forced off the continent. This led to a reliance on American loans.
This gave the Americans leverage over the British when the war was done. After the war the British were forced to make the Pound equally tradable with the Dollar, so the share of the Pound in international trade plummeted.
The Blitz devastated the country and many industrial areas.
All these factors led to the UK taking a much more reduced role in international affairs and the beginning of the welfare state that has remained until basically now.