There are many opportunities for cross-border co-operation. My experience really emphasizes much more the work with research rather than with other governments, so I can't really speak to that direct experience.
I've certainly witnessed an awful lot of transboundary co-operation that our colleague from the Nature Conservancy could certainly speak to in more specific detail regarding management of protected areas that essentially span the international border.
We also see many instances where states and cities that straddle the border remain aware and highly co-operative regarding transboundary issues. One of the ways in which we often see this happening out in eastern North America is through the work of the International Joint Commission that manages the Great Lakes Basin co-operatively and among many jurisdictions.