[throwaway154]

I assumed it was an Australian amalgamation of bush and whack that can be imagined to mean exactly what it means, like a lot of words do, perhaps inspired by a loose overheard memory, perhaps not.

I can't really imagine an American saying it. I can imagine an Australian.

[SyzygistSix]

People say bushwhack in the US. It means not using an established trail when out in the woods/wilderness.