It's a rural area. If you like the bright lights and city life, then it's not for you.  However, if you like outdoors, hiking, fishing, hunting, camping, and so on, it sounds like a great place. 

regarding point 2:

I would hesitate to consider any group of people to be  generally unfriendly, especially before visiting the area, but owning guns is legal in all states for citizens regardless of race. Carrying them on your person is legal in many states/cities with a permit. 

3) Except for large cities, most American cities have little to no public transportation and because the towns and cities are so spacious and spread out, getting around without a vehicle is not realistic. Smaller cities and towns rarely have taxis, and will not have any other 3 wheeled taxi bikes or motorcycle taxis either. 

My hometown is about a 5-hour drive from Sioux Falls (haha, which is basically like visiting your next-door neighbor in the heartland). I've only visited there twice before, so my opinions might not reflect the true nature of the place, I was just a traveler, there for a few nights.

1. Boring yes. Poor-not really, especially when comparing it to somewhere like Anhui. Though you won't see Mercedes on every corner, you will see a car in every household, likely two. I think the city is actually quite beautiful and has some nice natural falls on the river and city parks.

2. I remember the first time I came to China, my students asked if I needed to wear a bullet-proof vest to go outside! lol...I don't know if the Native Americans possess anymore than any other group of people, I doubt there's much difference. For example, my family lives in rural Nebraska and has 5 or 6 firearms in the house, even though we do very little hunting and sport shooting. Don't sweat this detail of your trip. Just because people can walk into Wal-Mart and buy a rifle doesn't mean they're going to walk out and start shooting people, owning a gun won't automatically transform them into a cold-blooded killer.

3. I don't know what the public transit is like there, it's been a decade since I was last there. Odds are there are city buses, but like most mid-tier midwest cities, they're likely not as convenient or cheap as what you're accustom to. I would be rather surprised if they had much for taxis. Plan on learning to drive or quickly making friends with someone who can, or else plan on buying a bike. America's midwest has space, space, space, and very few people. My hometown has 8,000 people but spans over 18km north to south.

All that said, what you've heard about it being poor and troublesome probably is in connection to common-held opinions of indian reservations. The rates of crime and poverty are often higher on reservations, near Sioux City in particular, I don't know... The few Native American friends I have are quite kind and have a kindred spirit that reminds me of many of my Buddhist friends. But, there are always bad apples, no matter what ethnicity.

The winters will be cold and snowy (not like Ningbo's snow, we're talking real winter weather, you'll experience at least 20cm snowfalls, -20C is not uncommon either, and Oh God that wind!) but when Spring arrives it makes you much more grateful to see green again.

What university are you looking at?

I love outdoors!!That sounds awesome!!

Hey Brent ,thanks for sharing me with the information and I really appreciate it:)

1)Just forget about the" poor" issue and I really should not mention it.I looked at the website introducing things about the city that it's a scenic while it's not populated.

2)As for the american indians ,I think as long as I keep friendly and not offend them ,it should be ok.Just a little scared that I never saw a gun in real life.."owning a gun won't automatically transform them into a cold-blooded killer",yeah,you are right,I might be too sensitive.

3)I am planning to buy a bicycle if it is possible so I guess it would be quite different from china where there is people.people,people...andn people.

I am accepted by "Augustana College" ,Have you heard about that before?It's a private liberal art college affiliate with Evangelical Lutheran Church though I am not quite sure about what does that mean but I guess it would be funny and interesting to take part in some church activities.

The school has only few chinese students and mostly are white americans so I guess I need to gather as much information in order to be well prepared as possible.

I am not afraid of the winter,haha.I have been to "ChangChun City " last octorber where is in the northeast of china to take my TOEFL test and wind there..ziiii...just like a knife stabs my cheek so that I guess I could handle the strong wind.It would be nice to experience the real snow (emm..imagining..lol)