If we understand a coup as an abrupt change in the political order, with some degree of popular support and with social and economic impact, led by a determined group of people with common interests, against the current legal and constitutional order (although it is common to find historical examples in which the laws and the constitution are 'bended' to fit the context), has there ever been such an event in US history? If not, what may explain this? Has there ever been any notorious attempts? (I'm from Brazil, and we had plenty of coups and failed attempts throughout our history).
In short, no. It was established that America could function without coups after Jefferson was elected president peacefully (sometimes called the jeffersonian revolution). However there was a conspiracy called the Business Plot. In 1933 Major General Smedly Butler was supposably approached by Gerald P. Macguire to join a plot consisting of business men and a 500,000 private army headed by Representatives John W. McCormack of Massachusetts and Samuel Dickstein of New York. They wanted to establish a fascist government and overthrow Roosevelt. General Hugh S. Johnson, former head of the National Recovery Administration, was to be installed as the ruler. This plot was supposably backed by Chase Bank. No one was prosecuted and everyone who was a part of it denied it's existence. It was considered a big hoax but after a 2 month investigation evidence suggest it might have been considered. But no one knows.
Edit: I was checking myself while i was writing this. It took more than 13 minutes so i didnt see the other post, my bad.
Actually, yes there has been at least one notorious attempt. While everyone remembers that John Wilkes Booth shot Lincoln, few know the full design of the operation. At the same time as Booth was to kill Lincoln, George Atzerodt was to kill Vice President Andrew Johnson and Lewis Payne was to kill Secretary of State William Seward. However, Atzerodt backed out at the last minute and Payne's attempt failed to kill Seward.
Clearly this was an attempt at cutting off the head of the government however, the identity of the designer (if there is one) and the goals delves into the realm of conspiracy. If Booth sympathized with the South, one would have thought he would have gone after Grant, general of the Army that defeated them or Stanton, the Secretary of War. Lincoln wanted a lenient reconstruction plan that had "malice towards none, with charity for all". In addition, Seward, who sided with Lincoln on the treatment of the South, wanted reconstruction managed by the State Department instead of the War Department.
Had Lincoln, Johnson and Seward died, Lafayette S. Foster, a Republican, would have become President and Stanton and the Republican controlled Congress would have taken over reconstruction and morphed into a means to punish the South. There are other "oddities" but in short, there is quite a bit of smoke to suggest that Stanton was attempting a coup d'etat.
There have not been any coups in the US. Why? Most historians will point to the 1783 Newburgh Crisis or Conspiracy as the seminal moment that reinforced the American military's professionalism and subordination to civilian rule. This was the closest the country came to such an incident, and there hasn't been another attempt since.
You can find good summations of this issue here: https://www.reddit.com/r/AskHistorians/comments/1lvibd/how_is_it_the_united_states_has_remained_coup/ https://www.reddit.com/r/AskHistorians/comments/1h69l8/military_coups_are_common_in_many_parts_of_the/