> MtGox existed because it is nearly impossible to open an exchange in the US.
That's kind of orthogonal to the issue of whether bitcoin can be regulated (it can, but that has little do with why exchanges in the US are legally difficult.) An exchange that trades bitcoin for boring fiat currency has to manage and distribute funds from fiat currency accounts, and its US regulation of that activity that produces a significant compliance cost to running an exchange in the US.
That's kind of orthogonal to the issue of whether bitcoin can be regulated (it can, but that has little do with why exchanges in the US are legally difficult.) An exchange that trades bitcoin for boring fiat currency has to manage and distribute funds from fiat currency accounts, and its US regulation of that activity that produces a significant compliance cost to running an exchange in the US.