I’m far from an expert, but can the US Fed really print more money? Didn’t I hear that something like 30% of the USD in circulation today didn’t exist at the start of 2020?

It has to stop somewhere. Doesn’t it? (Genuine question!)

The limiting factor is inflation!

If we get massive deflation from a “dollar short squeeze” (which I don’t actually think is likely but it’s what OP was suggesting) that means we need more inflation, which printing money would produce.

Printing money doesn't necessarily create inflation if it doesn't go into circulation.

My understanding is that "printing money" with a jobs program would be more effective at stimulating spending that, say, "printing money" with cheap interest rates (which might just mostly ultimately go into people's bank accounts as they sell assets to people borrowing the cheap money).

This is just treating a symptom, and not the underlying cause(whatever that may be).

When the symptom is having too much money to spend, it isn't clear that you want to "treat" the cause in the first place!

Well, it doesn't _have_ to, ask Zimbabweans. But there are real reasons they would not want to print forever.

QE and printing are different though

Not in substance.

What is the difference?

QE injects money via purchase of bonds / assets.

Technically it doesn't stop, but they are optimizing a complex system, and want to mitigate negative effects on their measures.

Generally speaking the vast majority of money is created by the private sector and not the government. For the Fed to be able to "fix" this by printing more money would already represent a large systematic change. This isn't impossible but fending off a deflationary shock is far more complex than people tend to assume, I think in part because of underlying assumptions that the majority of monetary creation is done by the government when in fact that may not be the case.

That's exactly why they're printing so much money. Deflation would cause a deflation spiral - i.e. a short squeeze on the dollar. They can keep doing it, but it's basically a mass-scale confiscation of assets from people. Not sure if that's the goal.

Apparently in the age of WSB apes, everything is a “short squeeze”. Even GME wasn’t a short squeeze (the SEC report clearly presents irrefutable evidence) and neither is deflation.

Why not just aim for 2% inflation like normal?