World War II was about many different things. I am not talking about why it happened, but about how. Opposing sides used directly competing philosophies to aid their effort. On one side you had Racism, the other Diversity.
The Axis ( Germans, Japanese, etc) used a philosophy of racial superiority. By teaching their citizens that they were superior and everyone else was inferior, it gave moral excuses to allow the invasion of other countries and the horrendous treatment/genocide of those deemed 'inferior'. The problem is, once you conquer your enemies, discrimination makes assimilating them very difficult. For some reason, the Jews did not do as much for the German war effort as black Americans did for the American war effort.
The Allies (Americans, Russians, British, etc.) used a philosophy of "All men are created Equal". Note, the communists did a lot of things wrong, but they were all for equality. As such, the Allies were able to cooperate a lot better, even though the capitalists hated the communists and vice versa. The US supported the other allies via the Lend Lease Act even before it joined the war. Navajo Indians were an important part of the war effort. We had active black combat soldiers, pilots, and sailors. Their were no Jews fighting for Germany in WWII.
World War II taught the United States the true value of some of the principles it was founded on, but had ignored. As we learned those values and took positions of power, it enabled the Civil Rights movement which eventually led to an African American President (Note, in general I have objections to using the words African American to refer to "black", - not all black people are Americans. But in this case the term is particularly appropriate, considering his citizenship - native born American with a Kenyan father.)
While the United States of America has made great strides in racism (African American President for example), it still exists. There are still many people in America that do not want an African American as President, even if they totally agreed with all of his political goals.
So where are these people? Where are the pieces of trash spouting "n!@@3r"? Well, America has mostly wised up enough not to use that word (obviously, even I am hesitant to spell it). There might be a couple of hundred Americans stupid enough to use that word when referring to the President, but not thousands. But that does not mean there aren't racists out there. They generally are smart enough to use the words "African American" instead of the "N" word.
OK, but why aren't people saying that they they don't want an African American President? Well, just as most racists are smart enough not to use the "N" word, most are also smart enough to know that if they come out and say they don't like Obama because he is African American, they will be ignored.
Again, where are these people? Well, I think that some of them have realized that if they drop the word "American" from the phrase "African American", then a) they are pretending that reality is how they wish it was true and b) suddenly their objection sounds reasonable. After all, most of them wish that there were no black Americans and if Obama wasn't an American he couldn't be President.
Now, I am not saying that every yahoo that claims President Obama is Kenyan (African) instead of an American citizen is a closet racist. But I am saying that a lot people that are racists are using the birther stupidity to disguise their racism. They know they can't publicly object to an African American President of the USA, but they have no problem lying (sometimes to themselves) and objecting to an African President of the USA.
Over 90% of non-white votes think Obama is an American. That number roughly stays the same whether you are in the North, West, South, or anywhere else in America. But when you look at whites, you get regional differences. About 90% of whites living in the Northeast, Midwest, and West believe Obama is a citizen. But only about 47% of white southerns believe it. 23% of white southerns think he was born somewhere else, 30% are not sure. Source Lets assume that the 30% are just going along with the propaganda of their friends, and 10% are just hoax fools. To me that indicates that about 23-10= 13% of white southerns are very likely to be racists.
That is why the birther hoax continues to thrive. In addition to the 5-10% idiots that believe any crazy conspiracy, there is another 13% wants to live in a fantasy world where no black man could ever be President of the USA - because none of them would be citizens. But just wishing something doesn't make it so.
Obama is an African American citizen who was legally elected President. His mother is a relative of George Washington, the founder of our country. You can't get more American than that.