Having served on selection / ranking committees, I can tell you that correspondence from an applicant is rarely factored into the decision of where to rank a candidate. This is largely because programs never receive letters saying "thanks, but I'm not interested." So we're left with hundreds of letters saying "I will be ranking you highly." Thus, outside of showing 'good grooming' by sending a note thanking the program for a nice dinner and (possibly) a hotel room, it probably won't increase your rank. That being said, it cannot hurt. Also, preliminary rankings of candidates are usually accomplished shortly after the interview so they are fresh in the faculty's mind. Thank you notes are generally received after this meeting.
However, the flip side of this is that programs do like to know who is truly interested in their program before the final rank list is submitted. Here, actions speak louder than words. If one is truly interested in a program, it may be wise (although NOT mandatory) to visit for a ‘second look' and shadow a resident. This may be impractical and cost-prohibitive for many which is why not doing this won't count against you. But, if you really, really, really like a program, it may be worth the time, effort and cost. Contact your desired programs and see if they do this before the lists are due.
Finally, wherever you end up will become home and you'll probably grow to like it, if not love it. It's REALLY hard as a 4th year to know exactly what you want in a program, and as you progress through your residency you'll place importance on things you never thought about as a candidate.
So… Relax and let it happen because for the vast majority of you, it will happen. Enjoy 4th year! 👍👍👍