From what I've seen in Idaho there aren't any mega cities comparable to the ones you see in movies, but there are still some decently-sized towns, like Boise. Idaho does have a lot of farmland, but every state in the US has large cities somewhere.
I live right next to Idaho in Oregon in a small town. There's about 10,000 people but most of them live on the outer edges of the city or way out in the country. It's a small(ish) farm town. I've never really felt like I was missing out on anything living there. We had one high school, two grocery stores, and one theater. We're 20 minutes away from the capitol, which is where people go to get anything more than groceries or something. We have 3 stoplights and it only takes like 7 minutes max to drive from one end of town to the other. Our "downtown" is about 4 blocks long and 3 blocks wide. We live near a few tourist attractions and in the middle of wine country which is why so many people have moved there. It's a perfect amount of people though. Everywhere I go I see someone I know, but I also met new people all the time.
I've only lived in one small town (and it was voted one of the top 10 coolest small towns), so other towns may be different. It may take some getting used to but the community atmosphere and comfort of a small town is fantastic!