My history is not totally correct but I think this is the answer you are looking for...
White supremecy in Europe and America is not the same thing nor is it entirely different. It is said that human life first occured in Africa and as the African population grew in Africa white (or Aryan) men emerged from the hills of Eastern Europe/Scandinavia. These men migrated across Europe and the idea is that Europe bloomed from a nordic seed. Hitler believed that most of Europes modern (19th/early 20th century) problems were due to the migration of other cultures (jewish, gyspsies, islamic, etc.) and he believed that by ethnically cleansing many of Europes problems would cease. He also believed that a pure, nordic bred human was in almost every way more superior and well rounded than any of the other ethnicities of the world.
The Klan is a radical conservative fraternal organization that arose after the South's defeat in the Civil War. At first all it's member's were veterans and former slave owners who beleived that freeing the slaves would cause many problems for America. To entertain themselves they'd dress in sheets meant to represent the ghosts of the Civil War and ride on horse back to the homes of blacks to frighten them. Then they started to desicrate property and vandalize homes by doing such things as burning crosses in the people's yard. Then they became classified as a terrorist organization when they started to murder black's on a regular and consistent basis. The Klan's numbers grew as it became the popular thing for white men living in the South to join. Many business owners or farmers were black balled or excommunicated in their communities if the didn't join the Klan. It grew more racist as more people joined and today it has grown from a Franternal organization into a terrorist organization with some very radical ideas and interpretations of conservative documents.
The idiot redneck comment is probably aimed toward the modern Klansman. If you live in the South and your ancestors have lived here since before the war you have black and white blood flowing through your veins. My great-great-great grandmother was black and I live in Texas and I am considered white, and if my family was from somewhere like Alabama where there was a greater number of slaves then more of my ancestors would have been black, and America is a melting pot, without a doubt. People in America, and especially the South aren't just irish for instance, they're irish-french, or German with Spanish decent, or half latino half white which means they're probably 1/4 Incan or Aztec or Mayan, 1/4 Spanish, 1/4 Irish, and 1/4 pick any european country, so there is no pure blooded American. The new Klan ideology preaches that the white man is supreme in the eyes of a Judeo-Christian God and all other races were created with the intent to serve the white man. The only problem is that they use no other definition of white man besides someone who isn't dark colored. They also hide behind "Christian ideals" but don't consider Christ a jew, the king of the jews or anything besides white, when in the Bible it makes reference to Jesus's jewish ancestory and descendency from David, and even describes Jesus to look like a dark skinned, fluffy haired middle-easterner. The KKK often times will throw Hitler in the mix and fly swastika adorned banners but they forget to recognize that Hitler's ideal man deals with Europe and that there is no way for Aryan supremecy in America because the Aryan blood in white citizens is so "watered down".
The modern Klan is an organization that capitalizes on the ignorance of most poverty stricken, uneducated white males of the south while neo-nazism is more of a racist/radical philosophy that, although I know is very very very racist and I am by no means a racist and I think that everyone's equal so dont even start that, could be discussed intellectually rather than just put down due to it's heavy saturation of ignorance...