This is has been widely discussed before in threads about Common Core Standards and AP History changes. You can go review the previous threads for lots of links and details.
Let me use an obvious example; in N.C. the 8th grade social studies curriculum is about "North Carolina History". You would think that the state curriculum regarding North Carolina would include some reference to the Civil War. After all it was a pretty big event that impacted our state.
Here is the 8th grade North Carolina history curriculum -
https://files.nc.gov/dpi/documents/curriculum/socialstudies/scos/8.pdf The Civil War is not mentioned once.
As noted in other threads, the new Common Core Standards for history are not focused on remembering names, dates, etc. of history - these items are deemed irrelevant and are not tested against. Common Core Standards for history are focused on studying social trends and other "soft" objectives.