America's trade imbalance with Canada is basically crude oil. Which they get at a significant discount because it's much more expensive to export anywhere else.
America then refines it and exports it as finished product or uses it internally -- one of the reasons why America has relatively cheap gasoline prices.
This "trade imbalance" is a massive benefit to America.
I've seen this point in a few different places and I don't know that it's understood as widely as it should be.
So just to expand on why that's the case. As a net producer of energy right now, the US produces more than it consumes. This is why it get's pointed out, that as a net producer, the trade deficit with Canada is also a surplus (or reduction in deficit) on the other side with other countries. Yes it may not be the same physical barrel that is exported vs consumed, but in a fungible way they're commodities. If you separate out that portion, we (Canada) then buy more goods from the US then we sell. And that's also just the goods trade, not including services which the US also sells more of to Canada than the other way around.