I agree with all of the above.
You didn't overreact at all... you reacted to being put in a ridiculous situation.
I would definitely tell him you need a day or two to process WITHOUT contact. Set a time, if you need to, when you will call him to discuss it. Frankly, if he can't respect those wishes, there are deeper issues of control (his) lurking.
The fact that he didn't ask you about any of this is a big worry, and I would discuss this with him. Also, the fact that just because your bicurious, or even if you're bisexual (I am), does not mean you want to have sex with every woman, and definitely doesn't mean you want to have sex with someone you JUST MET.
I'm thinking perhaps there was some concern and wierdness on her part, and in order to make things "one big family" he thought that if the two of you met and hit it off it might resolve those feelings. Misguided, definitely.
My advice would definitely be to take a couple of days, then talk with him about all of your concerns. Write them down, discuss each of them and see what he says. Then you can decide how you'd like to progress.
But definitely don't beat yourself up AT ALL about your reaction.