Imperialism occurs when a stronger country takes over a smaller one.
Spain took over Latin America and gained a lot of power from it. They were the leading power in the 16th and 17th century. They took over Mexico. Because of this, America picked a fight with Spain and eventually one.
France controlled 1/10 of the Earth's land. These places were North and West Africa, as well as South-East Asia, with other conquests in Central and East Africa, as well as the South Pacific. They were the second largest colonial empire behind the British Empire.
Britain took over many areas. Britain made colonies in North America, the Caribbean, and India. This meant they owned the economy of many places. Places like China and Latin America.
Japan also hopped on the trend of imperials. They even had parts of far Eastern Russia. Japan had a lot of countries like Hong Kong, Cambodia, and large portion of the far east.