Any USD retrieved from TotallyLegitExchangeLLC up in Belarus could still be marked as tainted if most of its blockchain transfers volume originate from illegal

Any USD retrieved from TotallyLegitExchangeLLC up in Belarus could still be marked as tainted if most of its blockchain transfers volume originate from illegal activity, so I feel in practice you would be limited to a narrow band of exchanges popular enough to have legitimate traffic and yet still unknown enough that they're still under the radar of their parents countries and/or the US' financial institutions.