3. Some countries were on the side of Germany in one of the world wars, and
on the side of the USA in the other, What caused these countries to join the
sides they did in each war (and in one case to change mid-war)?

Countries that sided with Germany in World War 2 was Italy, Japan, and most people don't know but Sweden did trade with the Germans during world war 2. Sweden did not partake in ww2 but they continued trade with the Germans, Italy joined the war because they sought out land and colonies, Germany wanted to undo what the treaty of Versailles did and japan wanted to rule the pacific. The United States sided on both wars with the Entente who helped France and Russia fend off against Austria-Hungary and Germany. The United States joined after the Sinking of the Lusitania.

c.

worked constantly and gave many sincere speeches about the importance of independence

there were abundant sources of fuel nearby