There's no such thing as strongholds in people's lives or thinking.

The demons weren't concerned about being forced to leave the area. They didn't want to be sent into the Abyss.

(Luke 8:30-31 NIV) Jesus asked him, "What is your name?" "Legion," he replied, because many demons had gone into him. {31} And they begged him repeatedly not to order them to go into the Abyss.

No, evil spirits won't dominate a city if people let them into the church. That's ridiculous. There's nothing in the Bible to suggest that.

No, you can't drive through a city and know what kind of spirits are there. There are demons everywhere. The Bible mentions demons that were in charge of the demons in entire countries. It would make sense that there are demons at work at the city, county, and state level. As well as in universities.

There's no difference between spirits that are immoral or occult or those promoting different religions. They're all demons under the authority of Satan. Everyone of them wants people to be immoral, to be involved in occult activities and to follow other religions.