I would name three main groups who gained new opportunities in the US because of WWII.
Women
The workforce mobilization engendered by WWII in the US was staggering. Companies -- especially those involved in war production -- went almost overnight from posting signs turning away unemployed men to actively recruiting unemployed women. Even today's schoolkids have heard of "Rosie the Riveter," who became the archetype of female workers across the country. While the trend of women in the workplace retreated in the post-war years, it rebounded strongly in the 1970s and is an undeniable force today.
Veterans
During and after the war, veterans were a class of people that enjoyed never-before opportunities in the US. Through the "GI Bill," veterans were offered college loans and grants and other government subsidies -- most notably home loans at favorable rates and terms -- that no other sector of the population had access to.
Scientists
Before WWII, science was something seldom talked about publicly. Medical science, for example, was still so weak that it couldn't prevent or treat the influenza pandemic in the 19-teens. Medical science was phenomenally advanced during WWII. Sulfa gave way to penicillin!
But German scientists working in other fields figured out how to make unmanned aerial vehicles -- yeah, UAVs -- and launched them with aggravating regularity toward London, Antwerp, and other targets of opportunity. Thousands died as a result of this scientific breakthrough.
As science became the clear gateway to technological superiority among warring parties, nations courted scientists, much as princes court potential princesses.
Many of the scientists involved in the Manhattan Project had German names. That is because they were born and raised in Germany.
WW2 was fought primarily between two sets of adversaries: Allies & Axis Powers; Axis=Germany, Italy, and Japan VS Allies=US, Britain, USSR, China, Australia, New Zealand, Canada.
Mexican immigrants
US got in the war because of the bombing in pearl harbor.
Japanese and Chinese groups
The Puritans and the Pilgrims
House and Senate
B. Parties and interest groups
individuals and interest groups
As counter-intuitive as it might be, the two groups involved in the Arab-Israeli Conflict are the Arabs and the Israelis.
There are several groups involved in the middle east conflict. There are Shia and Sunni Muslims involved. The United States is also involved, as well as terrorist groups like ISIS and Al Qaeda.
Rome and Carthage
There are two ehtnic groups in the population of Rwanda, the Tutsi and the Hutu.
The two main groups were ethnic serbs and ethnic croads
europeans and native indians
The State Government and the National Government
There are two groups in the 2011 world cup.
Catholics and Protestants
The two groups fighting in the Trojan War were Sparta and Troy. I think other Greeks were involved as well as Spartans.
The Native Americans and the US Cavalry.