What is a good textbook for U.S. history? Preferably unbiased, with an emphasis on the history of liberty?

Most textbooks used in public and private schools are good enough to study for the SAT in U.S. History. There are political and economic questions on this test, too. I suggest you consult your school counselor for some study guides to the SAT U.S. History test. The SAT is prepared and owned by the College Board, and administered by the Educational Testing Service. They don't care whether you are for or against liberty or freedom. The questions are multiple choice.