Chapter books that we've enjoyed that show American culture and sites:
Stuart Little by E. B. White
The Cricket in Times Square by George Selden
Farmer Boy by Laura Ingalls Wilder
Brooklyn Bridge by Lynn Curlee
The Brooklyn Bridge by Elizabeth Mann
My Side of the Mountain by Jean Craighead George
Dr. Beaumont and the Man With the Hole In His Stomach by Sam and Beryl Epstein (great for both history and science)
Children of the Longhouse by Joseph Bruchac
Misty of Chincoteague by Marguerite Henry
Rascal by Sterling North (C, Y, YA)
Inside Out & Back Again by Thanha Lai
The Yearling by Marjorie Kinnan Rawlings (with a warning that there will be death and loss in the book)
The Story of My Life (Unabridged) by Helen Keller
Flying With the Eagle, Racing with the Bear by Joseph Bruchac
Indian Shoes by Cynthia Leitich Smith
Seven Wonders of Sassafras Springs by Betty Birney
Black Gold by Marguerite Henry
Dewey the Library Cat: A True Story by Vicki Myron
Indian Boyhood by Charles Eastman (this is the original book upon which the picture book version was based)
Brighty of the Grand Canyon by Marguerite Henry
Hoover Dam by Elizabeth Mann
Little Britches by Ralph Moody
Man of the Family by Ralph Moody
I have also found that there are many great, more advanced picture books for that age. For the USA, besides history (which you've already got covered), I like to include books about Native American culture as well as folk tales. Here are some of the ones about the USA that we've enjoyed:
The Blue Hill Meadows by Cynthia Rylant
Appalachia: The Voices of Sleeping Birds by Cynthia Rylant
When I Was Young in the Mountains by Cynthia Rylant
Muskrat Will be Swimming by Cheryl Savageau
Rainbow Crow: A Lenape Tale by Nancy Van Laan
When the Shadbush Blooms by Carla Messinger and Susan Katz
Time of Wonder by Robert McCloskey
Island Boy by Barbara Cooney
Miss Rumphius by Barbara Cooney
The Star Maiden by Barbara Esbensen
From the Land of the White Birch by Shirley Neitzel
The Legend of the Lady Slipper: An Ojibwe Tale by Lise Lunge-Larsen
The Story of Light by Susan Roth
Sequoyah: The Cherokee Man Who Gave His People Writing by James Rumford
The Opossum's Tale by Deborah Duvall
Dancing Drum by Terri Cohlene
Crossing Bok Chitto: A Choctaw Tale of Friendship and Freedom by Tim TIngle
Iktomi and the Berries by Paul Goble
Indian Boyhood : The True Story of a Sioux Upbringing by Charles Eastman, edited and adapted by Michael Oren Fitzgerald