Short answers, pulled from the story.
The oldest surviving example of a wheel and axle combination dates to between 3340 and 3030 BCE. This artifact was discovered in the Ljubljana Marshes of Slovenia and represents the earliest physical evidence of this technology.
The primary obstacle to the development of the wheel in the Americas was the absence of domesticated large animals capable of pulling wheeled carriages. The American bison was too difficult to domesticate, and the horse had become extinct in the region by the time of European contact.
When a 100 kg object is dragged for 10 meters, the work required can be as high as 4905 joules, but when placed on four wheels, the work drops to just 123 joules. This reduction to one-fortieth of the original effort is achieved by shifting resistance from the ground surface to the bearings of the axle.
The invention of the spoked wheel occurred around 2000 BCE within the context of the Sintashta culture. These earliest known examples were used to pull war chariots that eventually moved deep into the Greek peninsula.
The evolution of the wheel continued into the 1870s with the invention of wire-spoked wheels and pneumatic tires. These innovations reduced rolling resistance and improved comfort by utilizing tension rather than compression in the spokes.