Maggie's Farm

The US military is one of our most competent government agencies because it focuses on an appropriate government task: national defense. It may or may not be markedly efficient at the task, but I can't come up with a plausible private-sector way to guard the nation and project force in the national interest.
Public safety is the same kind of thing. Public safety means that any crime needs to be investigated and the offender brought to justice, if possible. The rich are in danger if the poor are in danger and vice-versa. Same with fire protection. So I'm fine with those who supplement public-sector safety with their own (local refineries have fire contingents, for example). But I am more than willing to pay tax dollars and to demand you do the same for police and fire. Same for courts.
Transportation infrastructure, things like roads and bridges, get into a grayer area. In early America, many roads were privately operated and funded by tolls. That worked better when 100 miles was a long journey and 20 mph was a high speed. I think publicly-funded roads are appropriate. Publicly funded buses are much grayer. Surely a private-sector profit-driven company could work out a profitable schedule of runs and equipment. Or maybe not so surely.
Charity seems like an area where local government should be a last resort, not first, and federal government not a player. Education -- maybe the government should provide funds but private providers provide the service. I dunno -- if public education is where single-payer healthcare is headed, there are worries indeed.