...the irrational fear that Moslems will act the way they usually do.... White supremacy says that whites are superior to other races and hence must dominate them. It targets Moslems, but also blacks, Hispanics, Asians and Jews. Islamophobia represents prejudice and hate against Moslems in Western and Hindu, Buddhist and Jewish societies.
Both are old views. White supremacy was the official view in the West for centuries and spawned great evils like colonialism, slavery, genocide and Nazism. It was gradually displaced to the fringes over the last century. But only the overt use of force against other races has declined. Non-violent racial dominance via socioeconomic policies continues, eg in the US under conservatives. So there is class-based economic exploitation at work via the unfair division of profits between capital and labour. Then there is social discrimination at and beyond work against weaker races and ethnicities of all classes. The two combine to privilege rich whites.