Second off, the author presumes that local politics are nonpartisan because the stakes are higher at local levels than at state and federal levels. I think the actual reason is that running a campaign at the state or federal level needs a lot more funding. The support of a political party's machine is necessary in order reach all voters and convince enough of them to vote for you.
Third, the author proposes to start at the state and local levels. The 50 most populous cities in the US are located in only 29 states (plus DC). A lot of states don't have cities.
I would characterize the following states as not having any cities to speak of based on the size and density of their largest towns: Alaska, Arkansas, Alabama, Delaware, Idaho, Iowa, Kentucky, Maine, Mississippi, Montana, New Hampshire, North Dakota, South Carolina, South Dakota, Vermont, West Virginia, and Wyoming. That's 17 out of 50; over 1 in 3 states.