I think that's right.
The very first thing to say about it is that the kinds of defence and security challenges on that side of North America are completely different from the ones in the north. What this means is that there are different services, departments, and agencies involved in those questions, and the institutional rules that govern their cooperation are different.
I think that more of the issues that are in play in the southern part of North America—and we'll call it that—are security issues, as opposed to defence issues. Again, there is a lot of room for defence assets to be made use of and for defence services to cooperate with one another across national borders, but these are, for the most part, security issues. They have to do with drug smuggling, illegal immigration, and those kinds of issues. There's a different array of partners involved in those processes and a different set of issues to be worked out.
I guess one way of connecting the dots between what we talked about earlier and what we're talking about now is that when we say “the defence of North America”, on most of the issues up until two minutes ago we meant North America north of the Rio Grande. When we talk about the defence of North America in that broader arena, there are all kinds of new political and diplomatic complications involved. Mexico's constitution sets all kinds of limits on what the military is allowed to do and what kinds of relationships they can have with other countries' militaries, so it's a whole different playing field now.