I completely agree with the domino effect comparison about financial crises and the economy. When banks fail, when the stock market loses investment or when the currency loses value, lots of other problems follow. And it all happens very quickly.
For example, during the 2008 American financial crisis, several major banks failed. As a result other banks stopped lending. It also affected real estate and people couldn't pay their mortgage. A lot of people lost their homes. Many other issues followed like the devaluing of the dollar, unemployment, etc.
An since the American economy is so important for the global market, our crisis quickly turned into a global financial crisis. Once something major happens, everything else seems to follow and it takes a long time and a lot of smart decisions to recover.