Possibly there's also another feedback loop in relation to US imports of commodities ... As dollar weakens, US$ costs of - for example - imported oil may rise. This would result in higher costs for many business (lower profits, so lower stock prices), and higher transport & heating costs for consumers (who therefore spend less, so lower profits for business, so lower stock prices).
Also, another angle ... a weaker dollar potentially weakens attractiveness of US$ as an international reserve currency; at some point (not there yet!), alternatives (like â¬) become more attractive; investors drop US$ bonds, bond market falls, US$ bond yields rise, stocks fall ...
