They could ban those donors from ever entering Canada but that's about it. If they successfully pull off equating the truckers with terrorists, then they could request the US extradite them but that's pretty far fetched. Then again, pretty much everything they've done has been far fetched so who knows what they'll try next.

I mean, Canada has jurisdiction over whether or not they can enter Canada, do business in Canada, freeze assets in Canadian banks, etc.

The whole point was controlling points of access for international funds (ie. the GoFundMe, GiveSendGo, crypto).