Why was Japan angry with the United States before the war?

Answer 1

It followed a long chain of events that had filled many Japanese minds with resentment and hostility against the Western powers in general and the U.S. in particular. The first came in 1853 when U.S. Commodore Matthew Perry confronted Japan with a squadron of gunboats -- the "Black Ships" -- that eventually forced Japan to open its ports and accept unequal treaties. Japan deeply feared being colonized and was shocked by this gunboat diplomacy into rapid industrialization and a desire to join the club of imperial powers, including their feast on China and other weak, resource-rich territories. Japan modeled its rebirth after the Western mold, and joined with Western powers in suppressing the anticolonialist Boxer Rebellion in China in 1900. But the Western powers ultimately didn't want to grant what Japan felt it deserved. When Japan asked for a racial equality clause for the new League of Nations at the end of World War I, the white nations refused. In 1922, when the major powers established naval arms limits in the Pacific, Japan felt humiliated again by being compelled to settle for a ratio of forces set at 5 for the U.S., 5 for Britain and 3 for Japan. Fanning further resentment in Japan was a series of racist laws in the U.S. enforcing segregation and barring Japanese (and often Chinese) from citizenship, land ownership and Immigration. Seeking to build its own empire, Japan started spreading its colonial muscle and bases abroad, only to meet resistance from rival Western powers. The U.S. engaged in hostile acts aimed at Japan before Pearl Harbor. Under a covert U.S. government operation, American pilots were being trained in China to fight the Japanese as "volunteers," but of far greater impact were the American embargoes on oil, steel and other vital products in 1940 and 1941 that, coupled with a freeze on Japanese assets, were choking Japan. America's sanctions against Japan were prompted not only by a desire to evict Japan from China and release Japan's grip on the vital raw materials of Southeast Asia. Americans were horrified also at the large-scale atrocities inflicted on Chinese citizens by the Japanese Imperial Army. So it was a chain of events, it wasn't just Japan deciding to bomb Pearl Harbor out of the blue. Pearl Harbor wasn't just sitting there minding it's own business, things happened to piss off Japan and they felt the need to send us a message.

Answer 2

It was probably because America had the power to prevent Japan from expanding their empire across south East Asia.