>When the Fed expands their balance sheet, what they're doing is replacing private-sector assets with liquid cash. Given that the stimulus is appropriate for the economy, this is all fine. It's not anything that future generations have to "pay back." And it's not going to cause a collapse of the dollar.

This is simply not true. The Fed is buying assets at a premium (otherwise counterparties wouldn't sell the assets to the Fed) and is effectively injecting money into the economy. This is a bailout as the Fed is making a liquid market (that otherwise would not exist) for assets, saving the balance sheets of firms. Future generations pay this back not through taxes but through inflation.

Whether or not the U.S. dollar will collapse or not is another topic, but what can be said is that it is not sustainable to continue bailing out irresponsible businesses like banks and others when they do not exercise good business practices like prudence, not being overleveraged, or having a buffer in case of lost revenue. The only way this ends is either a depression the scales of which we've never seen in history before (which would liquidate and clear out bad businesses), or a hyperinflationary collapse of the U.S. dollar whereby more and more money is injected to prop everything up. I'm betting on the latter as the former is too politically inconvenient.