Which nation inspired the US K-12 public education system? 

The US K-12 public education system was primarily inspired by the education system in Prussia (now part of Germany). In the early 19th century, Horace Mann, who is known as the father of American public education, visited Prussia and was impressed by their organised and efficient education system. 

He believed that the United States could benefit from adopting some of the same principles, including mandatory attendance, a standardised curriculum, and the use of trained teachers. Mann worked to promote these ideas in the United States, and by the mid-19th century, many states had established public school systems based on the Prussian model.