From what I know of the book, it was a critical success but did not resonate with the public the way Sinclair wanted it to. The government took notice and tried to better regulate the meat industry. Working people, however, were not drawn to it the way had hoped.
After the collapse it become a "democratic" nation so US saw it as less of a enemy. Also, it become a lot weaker so it wasn't as big of a rival or threat to the USA. Allowing it to trade and work together on major projects.
