I did say "Social security is bad enough, please don't expand it."
Luckily, most Americans have pensions outside Social Security, so you won't end up in a situation where nobody has a pension if it collapsed. It would still be bad, but not as bad as if the federal government had a pension monopoly.
More realistically, it needs to buy the hammer from a political donor, a family member or friend of a politician, or some other politically connected person. The hammer will cost many times as much as anyone else would pay for it, and may well be the wrong kind of hammer or otherwise defective, assuming it's delivered at all. If a bidding process is used, the criteria will usually have been designed to favour a predetermined winner.
I'm not alluding to a specific case, but I think it's a pretty good analogy for how contracted government projects are run in general (at least in the UK, but I don't see why it would be different elsewhere).
Maybe I should not have said efficiently, as it really understates it. It's like if someone gets hired to work full time and then only works 20 minutes per week. Is that person committing fraud or just inefficient? What if the person gives part of their salary to their boss to look the other way? What if the person is a company, their boss is a politician, and the money is given to campaign organisation?
There is no reason to believe government programs are ran efficiently or without large amounts of fraud and corruption. There has to be a reason it costs governments (including government contracts) several times as much to do things compared to the private sector and non-profits.
A federal system sounds like a horrible idea and a really dangerous single point of failure. The consequences of such a system collapsing would be apocalyptic, and forcing everyone into a single system without competition all but guarantees corruption and mismanagement. Social security is bad enough, please don't expand it.
Luckily, most Americans have pensions outside Social Security, so you won't end up in a situation where nobody has a pension if it collapsed. It would still be bad, but not as bad as if the federal government had a pension monopoly.