ELI5: Why did America all of a sudden hate China?[Update: Holy balls guys I didn't think this would blow up so quick. Thanks for the awards. ]

Hey guys, it's just a random 17 year old from Singapore. I'm just curious because people here don't really care much about politics in other countries. But all of a sudden it seems like Trump doesn't like China anymore? I remember he used to make lots of deals in China. And if they are going to war it's bad for me. I'd like to know why. Thanks!