I'll try to answer the second question first. Both during the Revolutionary War and, of course, during the War of 1812, the United States attempted to seize some or all of Canada. In addition, the Irish-American Nationalist organization, the Fenians, invaded Canada in 1866, in 1870, and again in 1871, though in each of these cases the actions of the Fenians were condemned and curtailed by the United States Government.
It's no accident that the two occasions when the U.S. Government was seeking to change its relationship with Canada involved full-scale wars. These wars, of course, were being fought against Great Britain, which was the 'owner' of Canada. It was precisely because Canada was not an independent nation, on its own, but, rather, part of the world's most powerful empire, that the U.S. Government was not inclined to interfere with Canada's internal affairs, lest it provoke a war with Great Britain.
In any case, by the beginning of the 20th century, if not sooner, the United States and Canada viewed one another as friendly neighbors and during both World Wars, through the U.S. alliance with the British Empire, Canada became a U.S. ally. During the Cold War, both the United States and Canada were members of the North Atlantic Treaty Organization (N.A.T.O.).
Now for your first question. It's a little difficult to settle on a specific number for the times in which the United States has been involved in the overthrow of a government in Latin America because, by their very nature, covert action is secret.
That said, I can think of at least two occasions when the U.S. indirectly contributed to the overthrow of a Latin American government. The first I have in mind took place during the Eisenhower Presidency when the U.S. backed the overthrow of the government of Guatemala in 1954. The second I have in mind was the overthrow of Allende in Chile in 1973 during the Nixon Presidency. In both cases, the C.I.A. and other intelligence agency's, working behind the scenes, provided support for elements within the nation in question who wished to overthrow their government in order to seize power for themselves. It's no accident that both of these coups took place during the Cold War. In each case, the United States ensured the replacement of a left-wing government by a right-wing government.
It should be noted that there are other occasions in which the United States attempted to overthrow an existing government, only to fail. First, the infamous Bay of Pigs invasion of 1961, in which the C.I.A. organized Cuban exiles into a military force with the goal of overthrowing Castro. Second, the use of the Contras during the 1980s in an attempt to overthrow the Sandanista Government of Nicaragua.
Regarding direct efforts by the United States to overthrow a government in Latin America between 1917 and 2017, I can think of at least three occasions when the U.S. sent military forces to 'South of the Border' to initiate political change. In 1965 the Johnston Administration intervened in the Dominican Republic to ensure that a suitable government was installed. In 1983 Ronald Reagan ordered the invasion of the island of Grenada in the Caribbean. And in 1989 the United States overthrew the Noriega regime in Panama.
Lastly, while Noam Chomsky certainly has a point regarding U.S. interference in the Nations of Central America, the explanation that the migration of refugees from these countries is a direct consequence of U.S. interference is misleading at best. These nations have had fundamental problems since they achieved their independence from Spain in the 1820s, problems that those in power have had little interest in resolving because the solutions would involve their giving up most of their power and wealth. The United States, by usually favoring those in power, has not helped things. But the United States is not responsible for creating the fundamental problems within these nations.