Countries that currently, or in recent history have depended upon the United States. Often used in an arrogant manner by some Americans who think that somehow showing support towards a nation should somehow give them a stake in that nation. Also often used by people noting that the culture of a country seems, or that a country shows a lot of support towards the US, or because of their cultural similarity to the US.
First usage: The United Kingdom due to the assistance from Americans in World War II, is sometimes a considered a 51st state.
Second usage: The United Kingdom is considered a 51st state due to their government's support of America in the Iraq war.
What some people call Canada. Actually, Canada is another country; the twin country of the United States of America, north of it. We don't live in igloos, either.
Brought to public attention by Bob Woodward and Carl Bernstein in the book on the fall of Richard Nixon, All The President’s Men, ratfucker was Nixon’s term for a political operative who sows chaos among opponents; an agent provocateur. It is thought to have originated among campus political rivalries at USC, and seems to have some usage in the US military.
Along with Nixon’s other ratfuckers, Roger Stone caused fights at otherwise peaceful Democratic Party protests to generate a false narrative that the Democrats were violent and dangerous.