Do we have the same restrictions against Canadian trucks?
No, Canadian trucks come into the US all the time. They are required to carry higher insurance in Canada than the US.
However, most states(except MI) do not allow b-train trucks.
This double trailer arrangement allows more weight/axel and a higher overall gross weight and length. This is the way most freight moves in Canada. So logistically it makes it more expensive to move product into the US unless it is on this rig arrangement. Therefore, they will often offload the freight at the border of the US and load it onto a different trailer set up to travel in the states. They will also split the load at the border and deliver half at a time.
The other configuration of a Tri-axle rig or Maxi is used in ME, OR , WA , ID , MT & ND. This rig is only allowed in these states and typically does not travel into Canada.