As the title says, what would be the effects on bitcoin if the US economy crashed?
Would there be a sharp rise, as lots of people would want to move their money out of the dollar and into something else, or would the price drop, as a large fraction of the bitcoin community is American?
There would be a sharp rise, yes.
A crash in U.S.dollar would be a reason to worry for many of the bitcoin users because the currency is a widely accepted medium of exchange in numerous dealings done on bitcoin. But actual happening would be people would start dis-investing from USD and bitcoin is likely to rise.