By "comprehensive" I mean a text that's both thorough and expansive, covering all ~250 years of American history. I've got no clue where to begin, and was hoping some historians here could point me in the right direction. Thanks!
The Oxford Series of American history will cover many of the periods in question.
I would go to any bookstore and pick up an AP US supplementary book. It isn't a full textbook but rather a thick paperback book that is very detailed in order to prepare students for the AP United States exam. Might also be worth your time to find a short intro to American historiography.
Just want to add that there is a great list over in the sidebar for books. Here's the link for North America
Don't forget "The peoples history of the united states" by Howard Zinn so you can balance all that imperialist propaganda with how real people actually suffered as a result of America's arbitrary policies...