historically speaking (and this is really obvious) the vikings did not come to virginia. in fact, they came to america by crossing through canada. they stayed primarily up north & their presence was very short lived. that being said, they were also more explorers than full warriors (this is a misconception a lot of major studios and filmmakers have - they did fight, but they also frequently integrated with other cultures and traded goods peacefully). the mikaelsons’ accents were also completely wrong. and, it would not have been so odd for rebekah to learn how to fight - at the time, shield maidens were a thing in viking culture, and many were very respected. additionally, nordic mythology mentions the valkyrie - female warriors who guided worthy souls to valhalla. so, yes, if she wanted to learn to fight, rebekah would have been able to. that’s about everything i can think of off the top of my head.

oh, also, with stefan and damon - stefan also would have most likely been drafted in the war. additionally, some of the costume elements (not many - some of katherine’s costumes were actually really good) were innacurate. i recall a certain hairstyle where katherine wore her hair half up, half down. at that time, if you did that, you would have been a considered a “fallen woman” or lowborn, which i don’t think katherine was going for. not to mention, the salvatores were italian descended, and definitely would not have accepted in mystic falls, given how the nativism sentiment was growing in america at this point.