The first time Claire went to the past in Outlander, she didn’t know it was going to happen. The second time, she had time to plan.
Claire knew in 1968 that she would go back through the stones to find Jamie. She knew the rough time period that she was going to, expecting to head back to 1766. So, she should have done as much research as possible about the time, including the wars to come, the herbs to use in medicine, and about different Native American tribes.
Yet she didn’t. Was that a flaw in the writing, or was it simply impossible for Claire to research so much.
Claire didn’t expect to go to the Colonies in Outlander
Let’s just start with one part of history she wasn’t going to look into. She made it clear that she didn’t expect to go to the Colonies. Jamie suffered badly from seasickness, and she didn’t think he would ever want to get on a boat to head out that way. The only reason that happened was because Claire and Jamie needed to save Young Ian. And they weren't planning to stay in the Colonies after saving him from Jamaica!
So, it makes sense that she wouldn’t research much about the Revolutionary War. She definitely wouldn’t have looked into anything about the South. Just as a start, that meant dealing with slavery, which Claire in both the show and books has made it clear that she is against. She would have likely wanted to head to the North if she had a full say on the matter, so she would have limited her U.S. research to around there. But there was just no need.
There wasn’t time to research everything in Outlander
We also have to consider the time period. She was traveling back from 1968. It’s not like she had Google at her fingertips to get all the information she needed. She had to go to where some original source material sat in libraries for some research. That would have taken up a lot of time, and she just didn’t have it.
When she decided against researching the Colonies, part of it was because of lack of time. She looked into Britain, France, and some other parts of Europe, knowing they were a possibility. Even then, she didn’t have time to look into everything.
She’s also human. Was she really going to remember it all? Can we be a little realistic on someone’s memory here?
It wasn’t a flaw in the Outlander writing in either the books or the show. In fact, Claire not researching everything was realistic for the time available and for the overall story.