Yes, but water traffic is much more flexible than other kinds, because there is no set infrastructure forcing traffic to certain ports, and second biggest is much more dispensable than first biggest.
The international crossing is there because that's where the market has dictated that it will be until Canada decides to spend trillions uprooting their industrial region and moving it elsewhere. Its so important that it be where it is that Canada is absorbing the entire cost of building a new bridge over the Detroit river. Once the bridge is built, the Detroit crossing will likely retake top slot again.
Bureau of transportation statistics.