Nasa wants to land astronauts on Mars by 2033
cnn.com
cnn.com
The technology, funding, and skills required no longer exist. The US would have to move the whole defense budget to NASA to secure enough funding, and there is not the reservoir of skills in manufacturing or piloting that once existed.
As proof, I give you the fact that the US has not been able to send astronauts to the ISS without Russian assistance in the last 8 years since the space-shuttle was discarded. (Plenty of time to build a new, temporary space-shuttle if the ability still existed.)
As well, there is not enough time available between now and 2033 to build the entire space-technology industries from scratch to full production.