Dear Ms. XXX,
Thank you so much for arranging the trip for me and taking the time to interview me for the X position in XXX City, CA this week.
I had a very pleasant time in XX area during the past couple of days. After talking with you and YYY, I am further convinced that my background and skills aligns well with your needs. Having learned more about XXX's workflow and the projects in XXX now, I am even more excited about the possibility of working for XXX than I was before the interview. I am more convinced than ever that I will contribute my skills and talents for the benefit of XXX.
Again, thank you for your time and consideration. I look forward to hearing from you soon regarding your final decision.