There is functionality built into Importacular to help organisations collecting address data from all over the world but using the same form. In some cases the state field is used for county or region. 
Importacular has some logic built in that says if the country is US or Canada (or the country is not specified but the RE instance is set to US or Canada) then the county field should populate the state field in RE. Equally if the country is UK and the incoming value should populate the county field. That way the org can capture one field and the data can be put in multiple places.

The way to avoid this is to check the box on the field settings as shown below:
This field appears on the county and state field settings.