Right, I can see what Incandenza is saying about the Meso-america bonus. It could probably go either way---I assume the current lean towards 3 reflects a desire for bonus diversity on the map (I.E. you have a bunch of two's already, and most likely didn't want to add another 2?). In addition to that, the map already seems to lean towards the higher bonus value (Chilean, Central Andes, Eastern Forest) so Meso-America probably has enough precedent for 3. But it is still something to consider, as Incandenza points out, because of it's starting position relative to other bonus zones.
As for the bridges---I like the style, though the color stands out. When you compare their "solidness" to the rest of the map (that is more mottled...the landscape, the mountains, the oceans) they look a little out of place. I'm not sure you can add the mottled effect to the bridges, since they are so small, but I'd like see if something can be done to bring them a little closer in feel to the mountains especially due to their dichotomy (but the landscape/ocean as well).