> "> Cities like New York, Seattle, Chicago and San Francisco have raised local minimum wages"
> "> Laws in New York, California, Connecticut, Illinois, Maryland, Massachusetts, and New Jersey will eventually increase minimum wages to $15 per hour."
> "I don't find this reasoning very convincing."
those are fact statements--what's to argue?
> "That's the basic problem with a federal minimum wage."
whether a federal minimun wage is good policy or not is certainly debatable. on one hand, states are the canonical unit of government and the fed should generally defer to states (other than for national defense and interstate/international relations). wages and cost of living does vary across states and even within states.
but trade (including labor, as a distinct market) is a federal concern because of interstate commerce and the interlinking of economies brought about by globalization. so it's not unreasonable to argue that the federal government has a stake here. you might argue that the fed should have differing minimum wages for different states, but that's fraught with political land mines too.