Its a bit unfair to compare the two countries, the USA was a very young country then, and had an isolationist policy. There was also the Monroe doctrine, you stay out of our Western hemisphere we won't bother with yours
The USA was a very young country in the early 20th century ? It had already colonised the whole continent from the east coast to the west coast (Alaska included). At the time of WWI, the USA was more populous than any European country (except the USSR).
i don't know much about some of these wars, what did they win in the 100yr War, was this just a series of wars, was the battle won by Joan just the last war / battle
The Hundred Years' War was a long series of battles in which the French got back nearly half of their country (all the west, from Gascony to Normandy) that the English had acquired through a few judicious political marriages. The Duchy of Burgundy, in the hands of the Habsburgs, also acquired tremendous power, extending all the way to the Low Countries (also by marriage), and allied itself with England against the King of France. The French managed to kick the English out of France and regain the control of Burgundy. This is basically how the feudal patchwork of medieval France became the strongest country in Europe by the Renaissance.
In the 15th century, French knights were the most powerful and respected knights throughout Europe. Hardly cowards. The Romantic image of the medieval knight is mostly inspired of the French knights, and even the term 'chivalry' in English comes from French (note that the English had a long-standing preference for longbows and crossbows, as they didn't like close combat).
France dominated Europe militarily from the late 15th century until 1870. Louis XIV defeated all of France's neighbours, which boosted his ego and the prestige of France across the continent, as far as Russia and Turkey. This is how Czar Peter I (later known as "the Great") ended up spending several months in France to study how the French had succeeded in becoming so powerful. He copied the French system and vowed to make Russia, then a desolated backwater, a great country like France. His palace in St Petersburg, the
Peterhof, was one of numerous European copies of Versailles. French became the court language of Russia and was also widely spoken at court and in upper-class and bourgeois circles in the Ottoman empire until the early 20th century, such was France's prestige, acquired by the arms during centuries of military campaigns around Europe.
Britain controlled the oceans and had more colonies, but in terms of military power on land, France was always stronger. At the onset of WWI, the British army was ridiculous compared to the French or German armies. The British had most of their troops sent around the world to manage colonies, and these men didn't need to same training or equipment as the French or the Germans, because colonised peoples were hugely inferior militarily.