I guess living in another region of the USA for nearly eleven years has made me accustomed to something -- standoffishness.
Iowans, in general, aren't really rude at all. They just don't commingle. At least, not the ones in the central Iowa area that I've spent my time in. You walk into a convenience store in Oklahoma or Texas, and other people will: hold the door open for you, speak politely to you and say "excuse me" if they walk near you, and strike up a conversation with you if the situation allows. In the same situation in Iowa, nobody speaks to you, nobody expects to be spoken to. Unless you're someone they know, they ain't talkin'.
Even when driving on a highway somewhere, people are friendlier. I thought it was normal to wave to oncoming drivers until I moved to Iowa and had to unlearn it. And in Texas, it's standard procedure on a two-lane highway to pull over onto the shoulder and let someone pass you if they're coming up faster behind you, just as a gesture of politeness.
It's something that struck me today when I stopped to fill the van with gas. I went into the store to get something to drink, and when anyone walked anywhere near me, they promptly said, "Excuse me" and I noticed it because it was different than I'm used to. Just a regional difference, really, but one that I have to say that I missed more than I realized. I've always spoken to people, held the door, etc., just because it's who I am and I don't even think about it. I wonder if it takes people by surprise when I do that? I've never wondered about that until now.