"Political corruption is the use of power by government officials for illegitimate private gain. Misuse of government power for other purposes, such as repression of political opponents and general police brutality " is not considered political corruption."
So Mayor Emmanuel's efforts to curb gun related violence through the use of Chicago's financial power to influence the economic decisions of private entities may be misguided, arrogant, ineffective or some combination of all three, but it is not corrupt.
Even with the current state of campaign financing, the US is relatively free of political corruption, at least compared to the majority of other countries in the world.
World Map Index of perception of corruption
As the map below, combined with the map above, demonstrate, government debt as a percentage of GDP and political corruption appear, with notable exceptions, to be inversely related.
Public debt as a percent of GDP (2010).
There doesn't seem to be much relation between intensity of corruption and the size of government as defined by % GDP.
Unsurprisingly, freedom of the press and freedom from corruption are directly related.
2010 press freedom index scores