I don't take any kind of perceived future threat of Canada being cutoff from the Panama Canal outside of its damaging/blocking by a hostile foreign power in a war as especially likely or serious to consider. It would be such a substantial destruction of our relationship that I don't think it would be recoverable, as the precedent set is beyond awful. Hence my comments about it being "out of the scope of reality", aka I don't view it as worthwhile to discuss otherwise we're far down a far deeper rabbit hole where basically anything is on the table.
If the canal isn't an option, the traditional route of transiting around South America is back on the table. It drastically slows the timeline for resource transfer over but it isn't exactly an insurmountable task.
If we do not send AOPS and/or MCDV's to Africa, we are missing out on a number of different substantial benefits for the Navy. It is not within the mandate or jurisdiction of the Coast Guard to go operate on these sorts of missions far abroad, so we would not be participating at all without the Navy. Navy personnel requiring training, qualifications and sea time, deployments like PROJECTION to Africa allow us to get people within the force what they need alongside building working relations with regional/foreign nations and helping people in the process while we're there. We aren't always required to be in Europe or Asia, so it's worthwhile in my opinion to use our ships effectively abroad to the benefit of all. This theatre isn't vital so if something more important comes up at the time, canceling the deployment isn't the end of the world, but I also wouldn't write it off as a waste of time either.