If they were it would almost certainly be through a front in such a way that it wasn't publicly known about unless/until a scandal broke stopping that particular incident. As to whether that's likely to be happening... I've absolutely no idea, for all I know it could be extremely likely, or conspiracy theory level.

I'm really very skeptical when it comes to the US. Why? It's very difficult for them to transport money since they're mostly shut out of the international banking system. Even when they get some access, it doesn't last long (see HSBC).

Another reason is I feel that most bribes in the US are more subtle: they're in the form of political campaign funding, non-profit funding, a future board member, and so on... You need access to the banking system to do that stuff easily.

The impression I've always had was that money laundering, as long as they dont mind losing a big chuck of their cash by doing it, is pretty easy - and therefore if they saw the value in getting it into a legal banking system (to lobby through a non-illegal front) it wouldn't be impossible, just more expensive than lobbying with legal money. But the extent of my knowledge on money laundering comes 30% from an old friend who used to work for a bank detecting it and 70% from breaking bad, so could easily be wrong!