The extermination camps were created specially for genocide, people were gassed there. In the concentration camp the people were kept there and forced to work, there they would die from disease, desnutrition, etc... During WWII United States didn't care a lot about all the people that were deported to concentration/extermination camps.
The refugee policy of the U.S. State Department (led by Secretary of State Cordell Hull) made it difficult for refugees to obtain entry visas to the United States.
The U.S. State Department also delayed publicizing reports of genocide. In August 1942, the State Department received a cable revealing Nazi plans for the murder of Europe's Jews. However, the report, sent by Gerhart Riegner (the World Jewish Congress [WJC] representative in Geneva) was not passed on to its intended recipient, American Jewish leader and WJC president Stephen Wise. The State Department asked Wise, who had almost simultaneously received the report via British channels, to refrain from announcing it.
The United States failed to act decisively to rescue victims of the Holocaust. On April 19, 1943, U.S. and British representatives met in Bermuda to find solutions to wartime refugee problems. No significant proposals emerged from the conference. In 1943, Polish underground courier Jan Karski informed President Franklin D. Roosevelt of reports of mass murder received from Jewish leaders in the Warsaw ghetto. U.S. authorities did not, however, initiate any action aimed at rescuing refugees until 1944, when Roosevelt established the War Refugee Board (WRB).
By the spring of 1944, the Allies knew of the killing operations using poison gas at the Auschwitz-Birkenau camp. Some Jewish leaders pleaded unsuccessfully with U.S. government officials to bomb the gas chambers and rail tracks leading to the camp. Even after the Anglo-American air forces developed the capacity to hit targets in Silesia (where Auschwitz was located) in 1944, U.S. authorities decided not to bomb the gas chambers or the rail lines. U.S. officials argued that U.S. aircraft did not have the capacity to conduct air raids on these targets with sufficient accuracy, and that the Allies were committed to bomb exclusively military targets to win the war as quickly as possible.
United States didn't cause the Holocaust. The Holocaust was something very bad that happened, and it was all crazy Hitler's idea. He though jews were the main cause that Germany had so many problems. Even though Heinrich Himmler had the main idea of killing Jews in gas chambers.
I hope this help you!!