It could go through ports in Canada or Mexico. It may sound counter-intuitive, but I don't think that possibility can just be dismissed without even looking at

It could go through ports in Canada or Mexico. It may sound counter-intuitive, but I don't think that possibility can just be dismissed without even looking at the data. I could imagine that things like legal stuff can influence the stream of goods, not just geography. For example, CETA was just signed while the larger agreement that would include the US now has no chance. I don't know if there is anything in there that might compel a US based company to move things through Canada (and their subsidiary there), but at least it has to be investigated, I don't think consequences of such agreements are immediately obvious, at least they are not to me. I also would not have dismissed air freight so easily. I would think that while it sure delivers a lot less mass I would assume the parts carried by air probably are much more valuable than what's on the ships, so in terms of monetary value I would not have been surprised to see a higher share. Just think of UPS and FedEx and their big fleets.