And we have the computing power for generalized AI now, but actually getting it to work and do what we want, turns out to be far more complicated. If we had dedicated the money and time necessary to make it happen, maybe, MAYBE, we could have pulled it off. But, nothing is that simple, and it isn't just the US, no one else has sent any living being to Mars and brought it back home yet either.

There are a lot of engineering challenges in sending people safely to Mars and returning them safely to Earth, far more than involved in the round trip to the Moon. The solutions to a huge amount of those challenges exist in a state more like "we think this will work, but we haven't gotten the money to test it out yet", instead of proven technology that can get the job done. Factor in the engineering principle that whatever your estimate of time and resources required is to complete the project, multiply that by 2, maybe 4, and you're going to be closer to reality.

People forget that accomplishing huge things is more than just the engineering and production involved. There are politics, logistics, HR, facilities, and PR campaigns to get support for funding a space mission instead of using those resources to solve other major issues that many would prioritize above space sciences.