As I understand it, this isn’t necessarily the case. I understand that the BBC actually investigated making iPlayer available in the US previously. The outcome was that cable networks told them they’d drop BBC America if it was to go ahead. For most networks in the US, BBCA sits in the middle tier - not a premium channel (eg HBO), but not in the basic package. It’s used as bait/value-add to provide incentive for customers to upgrade from the basic package. So for the networks, having the same content available online lowers its value.
This is the basic crunch when it comes to geo-free online streaming vs traditional cable networks. We (customers) want both models available to us, but the two are in direct opposition. And in this case, it’d appear the traditional model is still winning, since BBC International decided that preserving BBCA’s income was more important.
We tend to paint it as rather protectionist, but in most cases, the content-providers do have the option of walking. That they don’t want to, tells us that the existing model is still the more profitable. There’s not much we can do to fight it until this changes.