The Hundred Years War Between England and France lasted for more than a hundred years (1337-1453) of off and on conflict before England appeared to have been defeated. Any conflict lasting this long would cause changes, and the aftermath of the wars affected both nations.
The Uncertain End
While we now recognize that a distinctive phase of Anglo-French conflict ended in 1453, there was no peace settlement in the Hundred Years War, and the French remained prepared for the English to return for some time. For their part, the English crown didn't give up its claim on the French throne. England's continued invasions weren't so much an effort at recovering their lost territory, but because Henry VI had gone mad, and competing noble factions couldn't agree on past and future policy.
This contributed greatly to England's own struggle for power, known as the Wars of the Roses between the houses of Lancaster and York for control of Henry VI during his mental illness. The conflict was partly fought by battle-hardened veterans of the Hundred Years War. The Wars of the Roses tore at the elites of Britain and killed many others as well.
A watershed had been reached, however, and the French south was now permanently out of English hands. Calais remained under English control until 1558, and the claim on the French throne was only dropped in 1801.
Effects on England and France
France had been severely damaged during the fighting. This was partly caused by official armies conducting bloody raids designed to undermine the opposition ruler by killing civilians, burning buildings, and crops and stealing whatever riches they could find. It was also frequently caused by 'routiers,' brigands-frequently soldiers -serving no lord and just pillaging to survive and get richer. Areas became depleted, populations fled or were massacred, the economy was damaged and disrupted, and ever greater expenditure was sucked into the army, raising taxes. Historian Guy Blois called the effects of the 1430s and 1440s a 'Hiroshima in Normandy.' Of course, some people benefitted from the extra military expenditure.
On the other hand, while tax in pre-war France had been occasional, in the post-war era it was regular and established. This extension of government was able to fund a standing army-which was built around the new technology of gunpowder-increasing both royal power and revenue, and the size of the armed forces they could field. France had begun the journey to an absolutist monarchy which would characterize later centuries. In addition, the damaged economy soon began to recover.
England, in contrast, had begun the war with more organized tax structures than France, and much greater accountability to a parliament, but royal revenues fell greatly over the war, including the substantial losses incurred by losing wealthy French regions such as Normandy and Aquitaine. For a while, however, some Englishmen got very rich from the plunder taken from France, building houses and churches back in England.
The Sense of Identity
Perhaps the most lasting impact of the war, especially in England, was the emergence of a much greater sense of patriotism and national identity. This was in part due to publicity spread to gather taxes for the fighting, and partly due to generations of people, both English and French, knowing no situation other than war in France. The French crown benefited from triumphing, not just over England, but over other dissident French nobles, binding France closer as a single body.