The false cause fallacy assumes that when two events happen in immediate succession, the former event caused the latter. For example:
Immediately after lessening the border restrictions for immigration policy, crime rates have skyrocketed in the country. Why are we continually allowing more people in the country that cause crime and disorder?
This seems pretty reasonable that the cause of an increase in crime rate is due to the lessened restrictions of immigration, however, there are other factors that could have caused this event to occur as well. Mainly, the increase in crime is not necessarily from the immigrants. Maybe the country is in a financial downturn, there is a violent sub-cultural movement, or maybe the law enforcement hasn't been executing their authority correctly. In other words, the increase in crime rate after the change in immigration policy could be a mere coincidence.