Are heads of shrimps safe to eat in US

I discussed a similar subject in this question: What exactly is "Sushi Grade" fish?

Raw fish isn't safe to eat if it's just been sitting around. However, the raw fish used in sushi/sashimi has been frozen (typically flash-frozen) in order to kill any parasites, making it as safe as any other food.

Most distributors of sashimi also have their own methods and internal regulations to ensure food safety, but specifics are understandably hard to come by. Suffice it to say, it's far safer to eat properly-prepared nigiri or sashimi than it is to eat an undercooked hamburger.

It's quite common. I had Garlic Prawns (shrimps) in a faily exclusive restaurant in Darling Harbour (Sydney) last weekend, with shells still attached to the tail.

From what I can gather it's mostly about aesthetics. I suspect there is some truth in the idea that it gives the impression of more shrimp for your money as well.

Some also argue that it adds flavour during roasting or sauteeing.

It should also be noted that many people will in fact eat the tail. (The entire shrimp is edible.) It's not my preference, so a simple pinch at the base of the shell and the shrimp will slide right out. (They usually - or at least should - provide you with a small finger bowl filled with water, and sometimes a slice of lemon, when you're expected to remove the tail shells yourself.)