Hmm…I’m taking AP Euro this year too but, I haven’t had that much trouble, even though my teacher isn’t that great…maybe you need to change the way you interact with text? It could be that your approach just doesn’t suit your learning patterns.
If you’re studying a lot it could be that you are able to easily answer specific questions but maybe forget to zoom out and look at how things relate to one another. Really analyzing test questions might help too, be sure of what they’re asking you.
To prep for the exam you should get a review book…Barron’s is pretty good…and try to reevaluate your study methods.