The "could've only been funded via Bitcoin" part isn't even necessary. The US government is kind of crazy when it comes to terrorism. Any connection between Bitcoin and terrorism that gets a lot of public attention is likely to result in major legal problems. It doesn't matter whether or not the fear is well founded or whether Bitcoin's role was incidental. Look at how much pressure there is to crack down on encryption in general, and that would have far wider-reaching consequences than regulating a cryptocurrency only a tiny percentage of people actually use.