Hm....I don't think there's a currency out there being dealt into illegal activities. Anything worth a great deal of value is likely to fall into that category.
Any currency that has a value can be use for illegal activities so it's not with the money but with the users who are thinking
of using USD as a tool to run their illegal transactions. Cryptocurrencies can also be use for illegal transactions so there is no difference.
Even gold or diamond or any valuable asset can be used as long as it is a form of payment. USD is a valuable tool so as any other form of currency and it is not exempted from being use for illegal activities.
These dudes involved in such activities obviously know how they cover their tracks and if caught, apparently will face the law in whatever country they may be.
From OP's point of view, I do not see how it is particular only to US since every other country as well always end up having some set of crooks. The only difference is that US being a generally used currency for international transactions makes it more common for payment.