I'm not suggesting that match fixing(or point shaving or spot fixing) does not happen. There's a mountain of evidence to the contrary.
I just don't think there will be a massive increase because Americans sites allow gambling. Asian sites move billions of dollars a year in largely unregulated betting markets. Athletes that wanted to cheat could already do so in relative safety. They would be foolish to start cheating in a situation where both the likelihood of them being caught is increased and the consequences of them being caught is worse.
You don’t even have to match fix to alter behavior in a way that has a financial return for things like fantasy sports that are stat based.