We've used Oak Meadow off and on for years. I know we did 1st grade with those materials. We're working through 6th grade with my eldest currently.
As for your history issue, it depends on the year. Sixth grade, for example, is all about Ancient Civilizations. I don't remember it having any particular US focus. It starts with cavemen and moves forward.
I do like that Oak Meadow is not about promoting any particular religion. While touring the Ancient Civilizations we are studying Judaism and Christianity and Islam and many, many others...but from a social/historical perspective.
In other grades, maybe even 7th (can't remember...they all blend together if I do enough research) US history becomes a focus.
If you have other questions, please ask. While I am not an Oak Meadow expert, I'm happy to help where I can. We are more unschooling oriented here -- using curriculum when it suits us and never in a compulsory manner.