I just watched a news clip on local tv where the domestic violence court was working through a backlog of cases, and the women who had called 911, in many of these cases, each took the stand and announced that she did NOT get abused, hit, beaten, forced, nothing happened, she made it all up, they were just drinking, they were just arguing, they were just tired, she did NOT want to press charges, and she was only here because she had been forced by the DA's office to be here. (In other words, show up or go to jail yourself.)
And in each case, the judge gave the boyfriend some jail time. Writing a letter or something like that would be ineffectual and they've certainly seen it before. Refuse to cooperate, or at least show up, and they'll come after you. You should internalize this, if you call 911, someone goes to jail. And once it happens, you can't unring the bell. It's just too easy for the offender to talk the victim into dropping charges, recanting, pretending it didn't happen. They may try it with sweetness, or they may try it with genuine threats, but they almost always try it. This whole thing is about whether they can control you and what you do, and that's why the law is fixed so it doesn't do them any good to get you to drop charges.
If they believe there's enough there, they'll press charges. May not, in this case, however. I'm sure they see a lot of these vacation meltdowns, but you certainly can't do anything to influence them. It depends on what they saw and heard and found out that night it happened.
You can call yourself "stupidgirl" all you want to, but I hope you won't stay stupid. Something happened, you're denying it now, but it will happen again, and you need to end this relationship before there is another crisis. You probably won't have anything in common with your boyfriend any more if you stop drinking anyhow.