They helped the allies to win the war.
The United States joined the Triple Entente, as there were trade agreements to defend, mainly with England and France.
For the United States, the consequences were mostly good, for example: they became the greatest world power, their trade started to be valued and their army became the best in the world. There were also bad consequences, such as the loss of thousands of soldiers and the sinking of several ships, such as Lusitania. For Russia, the prolongation of the war caused serious problems such as the loss of immense territories, the death of thousands of soldiers and the paralysis industry. Food prices have risen and strikes have increased. The economic system has stopped in all sectors. This later caused the Russian Revolution.
