I don't mean to sound insensitive, but I highly doubt that writing to Trump personally would change anything. :/

I am not at all well-versed in politics, but surely it would take considerable time before Trump could implement the changes that you fear? He can't suddenly be like "Ok, obamacare/whatever you're concerned about is gone" and that's that. It takes time and the agreement of other people.

Breathe deeply. The world is not over yet. It's possible that many of his campaign promises won't come to fruition.