Why were the United States and other nations interested in Panama

The United States was interested in Panama because they wanted to build a canal there which would allow them to be able to trade more easily.

The United States established diplomatic relations with Panama in 1903 following its declaration of independence from Colombia. That year, through the Hay/Bunau-Varilla Treaty, Panama granted the United States rights to a zone spanning the country to build, administer, fortify and defend an inter-oceanic canal.