It would have been around 600m long which would have limited the size of aircraft that could be flown from it.
A prototype was built in Canada but the project was abandoned.
The pressures that could have led to a desire to build such a massive ship were solved by the very planes that would have been its raison d'être--large planes. As planes like the B-29 and B-36 came into service, the ranges that bombers could fly grew to over ten thousand miles without refueling. Similar advances were made with airliners. Having a few airbases scattered around the world was sufficient to place the entire globe within range of your bombers, so placing them on a ship was unnecessary. Later, mid-air refueling completely obviated the need for such a huge ship. Bombers could get anywhere they needed to go from virtually anywhere on the planet.
WW2 would've been the only era where building a supercarrier to launch bombers would have been necessary, but given the size and complexity required to launch and recover heavy bombers such as the B17, it was never considered practical. Not to mention that aircraft carriers are mobile, so if your aircraft aren't within range, you could always move your carriers to get within range.
As an example of why it was never really considered practical, consider that post-war long-range bombers such as the B-36 were invented during WW2 on the fear that Britain might fall and the US would have to launch bombing raids from the continental US.
When considering the lack of need, during WW2, Britain was jokingly referred to as the world's largest aircraft carrier. Heavy bombers from Britain and North Africa could reach the heartland of Germany.
And, in the Pacific, when the US retook Guam, Tinian, and Saipan, they had islands within range of the new B-29. It's always easier to takeoff and land on a piece of land rather than a moving airfield.
After WW2, the advent of modern aerial refueling, the development of super long range bombers such as the B-36 and then the B-47 and finally the B-52 pretty much eliminated the need to ever launch strategic bombers.
For heavy attack aircraft, the Navy did eventually have heavy attack aircraft such as the A-3 that could launch off its new supercarriers. However, inter-service rivalry with the Air Force meant that the AF had a monopoly on nuclear weapons and strategic bombing until the submarine launched ICBM was developed - which of course further eliminated the need for strategic bombing from a carrier. And as jet and aircraft technology improved, the need for specific heavy bombers/attack aircraft from carriers waned as well.
A prime example is the A-6 Intruder, a Medium Attack aircraft first introduced in the early 60s - its crew of 2 could carry an 18,000 lbs. bomb load at a combat radius of nearly 3000nm without aerial refueling. Consider that less than 20 years earlier, a state of the art B-29 took 11 crew members to carry 20,000 lbs. of bombs a slightly longer range with no option for aerial refueling at a slower speed. The advance in technology was extremely rapid.