Last summer I drove back roads of Nebraska to get to Agate Fossil Beds. There was grass from hither to yon, and I felt so relaxed, just looking at it. After I visited the park, I headed toward home in Wyoming, and it didn't take long before I ws driving through horizon to horizon dust, rocks and sage. I lost that comfortable feeling. I'm from Iowa, and I like to see lush fields, I was surprised at how my subconscious reacted to all that nice Nebraska grass. Thanks for those pictures.
Glenn Randall, in his fantastic book, The Art, Science, and Craft of Great Landscape Photography, talks about studies done using landscape photos to try to determine what we humans consider safe and desireable places, i.e., those most conducive to survival. These tendencies are probably determined by our DNA or maybe epigenetic DNA, but they gravitate towards grasslands with a few trees in the distance and a view out so we can see if any predators are coming. Water is also a requirement, generally, and smaller streams are best. I recall driving back from Alaska a couple of years ago and feeling the same way you describe when I got to the great Alberta prairies, a sense of being able to relax and not being on the edge.