Golden Blood is one of his earlier works, first published in 1933, and I picked a used copy of the 1964 paperback up somewhere because of the utter gawdawfulness of the cover.
So, here's the way this thing goes. All-American mercenary and general good egg Price Durand gets recruited by a greedy, obese and pasty-skinned Brit to lead a group of unsavory European soldiers of fortune and untrustworthy, shifty-eyed Arab bandits through the Arabian deserts to find a mythical city of gold, kill the inhabitants and keep the gold for themselves. When they arrive, they discover the Arab tribes in the area held in serf-like conditions by mysterious golden immortals with apparent magical powers, so rather than kill the Arabs like they had intended, they rally them in revolt against their masters and use them as shock troops. Meanwhile, Durand himself, with his red hair and All-American good looks, is immediately mistaken for the Arabs' legendary king reborn to lead them into salvation. And so on.
So, the hierarchy is set out pretty quickly, as the European adventurers are introduced. Northern Europeans are sensible, intelligent, orderly, though clearly not as good as the Americans (of which there are two) at being courageous and able to think their way through tricky situations. The southern Europeans are not as smart, more prone to bursts of emotion, more likely to fly into an irrational rage (as opposed to a righteous anger, which, combined with a good right cross, gets Durand through many a certain-death situation). They are tricky, unpredictable, and liable to turn on their friends in pursuit of immediate gain.
The northern Europeans, particularly the British (even though they are probably gay), are superior in this regard; their own double-cross is carefully planned in order to maximize long term gain. Only the Americans have no intentions of double-crossing anyone else.
The Slavs in the group are somewhat more bestial in nature than the southern Europeans. Especially the Montenegran, who is described as massive, strong and hairy, and given the nickname "The Black Ape," as that is what he resembles in both appearance and intelligence, incapable of independent action, and slavishly doing everything that the Spaniard tells him to do. Clearly Williamson wasn't aware that Montenegro means "Black Mountains" and has nothing to do with skin color, and created a strange race of black slavs.
When they meet the Arab bandits, it quickly becomes obvious that these folks are absolutely untrustworthy. They have evil shifty eyes and "swart" skin, and the whites know that they must always post guards at night to prevent the Arabs from cutting their throats in the night. Because that's what Arabs do. It's in their nature. But for all that, they are easily cowed by the white's weapons, particularly the tank that's being driven by the other American, Sam Sorrows, a spry old guy from Kansas with irrepressible optimism. I imagine him played by Sam "Sometimes You Eat the Bar" Elliot. The Arabs are cowardly, liable at any moment to throw their hands up in the midst of battle, clutch their heads while calling out for Allah to save them, and flee back to where the white people are bravely waiting for the Arabs to soften up the enemy.
Except, of course, for Aysa, the woman - oh, sorry, the girl - who wins Price Durand's heart. She's one of the tribal Arabs, and had been selected as a sacrifice to the golden immortals. She is brave and clever and beautiful and exotic - but not too exotic, as Williamson takes care to tell us over and over how white her skin is, and how unusual her blue eyes are in a tribe of Arabs who have been isolated from the rest of the world for at least a thousand years. She escapes the golden folks, is captured by the southern Europeans, who plan on raping her, is saved by the American (the northern Europeans think it's barbaric that the others are planning to rape her, but concede that she is their property, and so there's nothing they can do about it), is once again captured by the golden people, and then is finally saved again.
In the end, everyone dies, mostly from their own greed and stupidity. Except for Price Durand, the lovely Aryan Arabic Aysa, and, of course, Sam Sorrows.
So I read this book, wincing at the pervasive racism, thinking "Really? He really said that?" But what is most astounding is how matter-of-fact it was. He wasn't telling people anything they didn't know. The darker the skin, the less civilized, the less evolved. More of a nod and a wink, a nudge with the elbow and an exasperated you know what they're like. Thing is, I'm sure that at the time it was all completely invisible to Williamson, to his editors and publishers, and to his readers.
Makes me wonder what, decades from now, we'll see in our own words that we can't see now.