A glance at a map of the distribution of carnivorous plants in North America reveals that a large part of the continent is almost completely devoid of CPs. Here I've mapped the distribution of Drosera anglica (in yellow) and the genus Sarracenia (red).
As you can see, the entire central part of the continent, from the Appalachian Mountains to the Rockies, is completely bare of these species. This, even though historically that area encompassed a diverse array of habitats, including grassy plains, mountain glades, and meandering rivers.
Now, the impact of large, herd-forming herbivores on wetlands and other fragile habitats has been well-documented. Carnivorous plant habitats, too, have long suffered from the introduction of domesticated cattle. (I documented an example of the negative impact of these clodfooted composters here).
One wonders whether some prehistoric cousin of the modern Bos taurus might have decimated carnivorous plant populations of ore, turning once-lush marshes into dry prairies and restricting carnivorous plants to their present distribution? The American Bison, of course, springs immediately to mind!
This majestic lumbering ungulate of the American plains would have unleashed decimation on fragile wetlands! Although hunted to near extinction in the late 19th century, upwards of 60 million bison are thought to have blanketed the plains before the wholesale slaughter began.
Here I've mapped the historic distribution of the American Bison on top of the distribution map from above:
Interestingly, the outline of American Bison distribution follows that of the mapped carnivorous plant species quite well. Naturally, correlation does not indicate causation, but could bison have played a role in limiting the distribution of carnivorous plants in North America? Who knows...