Local - Schools, Police, Fire Dept
State - Criminal laws,
National - Court for cases between States, Protect the Homeland - Military, Laws that affect US citizens across State Political borders
Those are the only FUNDAMENTAL responsibilities/services that I can come up with.
Any more I missed?
The American social contract between the American government was written by Thomas Jefferson the line about inalienable rights life, liberty, and the pursuit of happiness.
Basically, as citizens we give up freedom to do whatever we want to be subservient to the laws of our nation.
In exchange, our nation forms a social contract with each citizen to work to benefit us.
Life, liberty and the pursuit of happiness are huge concepts that really does entail a government meant to help each citizen in those areas and that's big.
There will be disagreements about what big means in terms of government services, but really I haven't meet any people who actually disagree about what the government should be doing to help Americans.
The real disagreement in American politics is over "who" the government helps.
For millions of Americans, they truly believe that certain segments of the American populace are undeserving of government help, and they see the government helping those people as bad for this nation.