Great Wall of America

The Great Wall of America, also known as the Trump Wall, Mexico Wall or just "The Wall".

Pre-Asteroid
Built in 2018 under the Trump presidency of the United States of America. The wall stretches for around 3100 kilometers across the US-Mexico border. Contrary to popular belief, Mexico did not pay a single cent in the construction of the wall. The wall was supposedly built to "deter immigrants", however, its real function was as a secret refuge for the President, his or her family, and top government officials. An estimated 572 people took refuge in the Wall, whose descendants founded the United States of Aztlan as a successor state to the United States of America.

Asteroid and Post Asteroid
The Great Wall of Trump survived the asteroid impact, as well as the subsequent years of decay. It now only covers around 2300 kilometers as of current period due to disrepair. Currently enclosed inside the United States of Aztlan, it still marks the boundary between the more Anglophone northern part of the country and the more Spanish and Aztlanic-speaking southern part. It is also a major tourist destination, and several areas, along parts of the southern borders of California, Arizona and Texas, are kept well-repaired as a tourist attraction. However, other parts of the Wall are crumbling and face the same sort of disaster the older Great Wall of China had.