I have a county level dataset with a dichotomous variable which represents whether or not any charter schools exist in a county. I am performing a nested logistic regression. That variable is the response and the explanatory variables are social factors such as education level, language spoken at home, household type, etc. When I include all counties in the U.S. (Including ten states which have no charter authorization laws and thus every county in those states is represented as a zero in the response variable) my results show significant associations between the response and the explanatory variables. When I exclude those ten states the significance disappears.
Any ideas as to why this might be happening?