The crash would come from malinvestment that is caused by debasement via credit. If the purchasing power was adjusted instantly the moment you print another dollar bill (i.e. prices would grow the same second), then there wouldn't be any malinvestment - some people would simply lose or gain wealth.

However, owners of new money do not outbid savers on all markets in all products the same day. They go and invest in some particular market changing prices there. E.g. stock market, or housing market, or some foreign production facilities. The money slowly flows to more and more hands finally ending on high street and competing with all existing money there - prices grow, savings diminish, purchasing power of "regular" consumers goes down. But the investment was not accounting for that because it was not known how much and how quickly all this new money will come on the market. Especially if there are numerous capital controls and high friction: the money saturate some other markets for a while until on day X it flows to your market and destroys your business in one month.

Example: imagine you look at current price structure and expect that investment in iPhone factory will let you sell 1 billion iPhones and make some profit. You go and build your factory, pay your bills and finally after 1 year produce 1 billion iPhones. By that time all your investment money is being moved to hands of many private persons who drive up the prices on all goods in the markets they participate in. If they are on your market, bad news for you: food will be more expensive and people will spend less money on your iPhones; and you will go bankrupt (unless you borrow more of printed credit to stay in the game longer). In reality, it's more complex. Trillions of dollars are being held outside U.S. and do not cause enormous price increases inside (official stats say "1-2% inflation") because for foreign holders of dollars there are either no things to buy from U.S., or it's hard/expensive to do due to regulations, tariffs etc. So U.S. effectively outsourced destructive effects to other countries where people get poorer faster than in U.S.

The bad news: the longer you keep artificial barriers, the harder market will punch you back. The longer U.S. market does not see its own printed dollars, the more and faster these dollars will flood in on some random day when foreign economies will be so depressed, that they'd try hard to get rid of their greenbacks where they still have high value.

Then, of course, U.S. gov would disallow citizens selling stuff to "enemy" countries to prevent too many dollars increasing prices at home. This will effectively move country to a closed loop North Korea-style. No one outside U.S. would want to sell stuff for dollars, and americans won't be able to sell their goods to foreigners. Since most of the production is outside the U.S., country would need to build new factories inside. But to do that you need genuine savings. Since all savings are effectively destroyed, huge depression would be on the horizon. So the government would continue printing money, but this time it will go to the home market to build production inside. This will quicker lead to very noticeable inflation and even more bankrupcies and depression. The course of things can be changed by two means: either government intervention will be stopped (e.g. people make a bloody revolution or they switch to Bitcoin), all losses are accepted and people can start saving agin. Or government begins another war and forces other countries to accept dollars and produce stuff for U.S. But that can be done only to the extent on how many productive facilities other countries have and how much can they protect themselves. If the war path continues, it'll be just a misery everywhere until USG has nowhere to go and collapse after too much destruction.