Really? The USA wanted to stop the Russians from taking over Japan like they did in Eastern Europe? The Russians have taken over an island from Japan and they're are still there. And the Russians in Eastern Europe. The USA allowed them to be there. That is why the US army was quickly sent back to the USA after the Second World war. If the Russians had invaded the rest of Europe than no army was there to stop them.
While you are correct the Russians are in control of islands north and northeast of Hokkaido. You are incorrect about almost everything else. The United States sent every military unit sans 5,000 troops to the Pacific theatre after the Victory of Europe. This was to make sure that World War II did indeed come to an end since the United States were in desperate need of reinforcements.
Yes Russia does control one of the Japanese Islands, The Island of Sakhalin, which is north or Hokkaido, and they did invade two days after the United States dropped the bomb on Hiroshima. The Soviet Union declared war on Japan that lasted three weeks (August 9th to September 2, 1945). The Soviet Union did not "take over" more than take back what the Japanese had originally been controlling. Japanese puppet state of Machukuo, Mengjiang (inner Mongolia), Northern Korea, Karafuto (Commonly known today as South Sakhalin) and Chishma islands (also known as Kuril Islands)
There is a lot of debate on who really should own the Kuril islands since they are in between the Sea of Okhotsk and the Pacific Ocean. The islands stretch from Hokkaido northeast to Kamchatka, Russia. This is not the first time Japan has disputed with another country about island ownership, Japan and South Korea are still disputing who owns Dokdo, but that is a different matter entirely
During the entire course of World War 2, the Soviet Union had military occupation of 11 countries: Norther Iran (1941-1945), Hungary (1944), Romania (1944), Bulgaria (1944), Czechoslovakia (1944), Northern Norway (1944-1946), Germany (1945), Austria (1945-1955), Manchuria (1945-1946), Korea (1945-1948), and Kuril Islands (1945)
All of these European countries were under attack to become Soviet Satellites under Operation Barbarossa.
Northern Iran was fought alongside the British to secure the oilfields and to secure supply lines for the Soviet Union
Soviet presence in Hungary lasted until 1991
The initial focus on Romania was to turn them from Axis to Allied. Troops were stationed there from 1944-1958
On September 5 1944 Soviet Union declared war on Bulgaria and on September 8 1944 Bulgaria declared war on Germany. A new government was appointed on September 9 and Soviet troops left in 1947
Soviet Union controlled East Germany. When East Germany and West Germany were reunited, Soviet Union signed a treaty to withdraw all troops by the end of 1994
While the Soviet Union did declare war on Japan and control Karafutp and Chishma Islands, it was not until the Potsdam Declaration that stated " Japanese Sovereignty shall be limited to the islands of Honshu, Hokkaido, Kyushu, Shikoku, and such minor islands we determine"
One thing that people do not realize is how terrible Japan actually was during World War 2. Just look up Unit 731 to see for yourself the terrible nature that Japan was creating.