History has certainly proven that American presidents need some pretty security, and Cadillac One is just the vehicle for the job.
There was quite a lot of hubbub back in 2009 when Cadillac rolled out its new presidential limo, and almost all of it was written either by or for people unfamiliar with armored cars. In truth, the currently-serving presidential limo isn't especially remarkable for a car belonging to a head of state. It is a one-off and in this sense it is unique, but the ability to repel rocket or chemical attacks is nowhere near as unique as the press may have led you to believe.
Just as we found with the popemobile, presidential vehicles existed for a long time before they ever became armored vehicles. William McKinley was the first president to ride in an automobile, but the first one to actually own one was his successor, Theodore Roosevelt. This was a white Stanley Steamer, and the next presidential car would actually be steam-powered as well. But it wasn't until 1939 that the first car was built specifically for the president, a V12 Lincoln convertible for Franklin D. Roosevelt. This had some security equipment but was ultimately deemed unsuitable in 1941 after the attack on Pearl Harbor.
Basically, the Secret Service started to become increasingly concerned about assassination attempts. Needing something more secure, but without many options on such short notice, the Secret Service acquired an armored 1928 Cadillac 341A Town Sedan for presidential use. Interestingly, the car had previously belonged to Al Capone. By the end of the war, the original Lincoln had been modified into a rolling fortress, and would remain in service until 1948. But after this, security became something less of an issue, right up until 1963. That was the year of the Kennedy assassination.
Thus began the era of the enclosed and armored presidential limo which continues today. But even Nixon had a sunroof which allowed him to stand up and wave, and security didn't reach its current level of seriousness until 1981. It was in this year that there were assassination attempts at both President Ronald Regan and Pope John Paul II. Neither of these two had been in a car at the time, but it was clear that members of fringe political groups and lone weirdoes would be taking potshots at politicians as a pretty much regular thing from this point on, and more security would be necessary.
At the time, Regan was still using an armored car originally acquired under Nixon, and an interesting footnote to the assassination was that the bullet had actually missed Regan, hitting him only after it ricocheted off of the car's armor. Presidential vehicles are now purchased much more frequently as a means of making sure that the security equipment is state of the art and in working order. Thus the 2009 Cadillac One. Built on a truck chassis but with a body meant to resemble a mainstream Cadillac sedan, this is still the current presidential vehicle.
Advanced as this technology is, things like the positive pressure system and oxygen supply to ward off chemical attacks are pretty standard things on cars owned by world leaders, and the ability to stand up to an RPG attack isn't so rare either. In fact, there are thousands of vehicles with B7-level armoring just in the United States. Most are owned by security firms, but there is no shortage of such vehicles in the hands of private citizens. The price of Cadillac One, estimated to be about $300,000, has been talked about at length as well, but when compared to the $1 million+ vehicles driven by some world leaders, it's actually a decent bargain.
It can be compared prisewise to the Conquest Knight XV, another $300,000 armored car that's actually one of the cheaper vehicles featured in this series. So Cadillac One might not be all that unique, but there is no denying that it's a hell of a vehicle.