This seems like a stretch, to me.
They would trade for those raw materials and finished goods that they want to use, but don't have much of, in exchange for those raw materials and finished goods of which they have surplus. Just like everyone else. Being dragony has no effect on that, at all.
Regardless of what you think about the logic of them having built a human like society and culture, they clearly did, so they would interact with other nations in much the same ways that human nations do. Or elven nations. Or Dwarven ones.
Also, many people travel because they want to, and this has been true in literally every era. It's more true now that ever before, sure, but even in the so called Dark Ages, people left home on merchant ships to seek their fortune, and often found some foreign shore upon which to "go native", and/or brought some part of their family with them to some foreign land, once they'd made the contacts and gathered the resources to do so.
Why shouldn't dragonborn do the same, especially in the 100 years where they had a fairly powerful, quite stable homeland, and plenty of their own kind in other lands?
And in their current state, yeah, they are definately going to be trading, engaging in diplomacy in foreign lands, etc. It's more reasonable to see a Tymantheran DB in Waterdeep than to see someone from most places east of the Heartlands, because Tymanther needs support, resources, allies, etc, and they aren't going to get it by having every single DB in the Realms hunkered down in trenches.
I strongly doubt it.
Humans have short memories, and are quick to make friends and enemies. And the various novels make it seem like humans aren't really all that enamored of elves, on the whole, IMO.
Also, I don't think that any FR novel I've ever read touches on human civilization being built with the help of elves and dwarves, etc.
First, I don't think they have a 'quite stable homeland.' They have a homeland that has been dropped into another world, where they have developed a reasonable trading relationship with one neighbor (High Imaskar), who happens to be in constant battle with their other neighbor (Chessenta). In terms of their relationship with Chessenta, in the campaign guide it's all good, but in the one novel that I think it has any information (Whisper of Venom), they are moving toward war. With their other Returned Abeir neighbors, they have poor relationships. In addition, they landed in a portion of the Realms that has a history of being isolationist, being in perpetual conflict with their immediate neighbors, and little contact with the rest of Faerûn. Their primary focus, aside from the relationships and conflicts of these immediate neighbors is hunting down and killing dragons. While this in itself would be viewed as heroic by other civilizations, it doesn't really build political relationships. Adventurers are rare to begin with, and while a single dragonborn might be met with indifference, or even intolerance, a group of them, armed for battle, coming into a town would probably be somewhat alarming. If you're a farmer in a small village and a half-dozen or more heavily armed 7' tall draconic 'men' wander into town, I don't think you'd find it normal.
The elven/human connections are well documented in Realms supplements. Myth Drannor and Silverymoon are two examples, later Illefarn, etc. The rise of Netheril was directly because the elven nations taught the humans magic. The major exceptions being the Old Empires (humans from another plane) and Calimshan.
And you're right, in general the humans, elves, etc. do have somewhat reserved interactions. Again, humans are predominant. Waterdeep is 64% human, with elves (mostly moon) and shield dwarves around 10% each. Lightfoot halflings and half-elves 5% each, gnomes 3% and half-orcs 2%, all other races are 1% of the population. It's one of the most accepting of cities. But Waterdeep is a long way away, support, resources and allies need to come from much closer to be in sufficient amounts, and for a reasonable price. That means by ship from any number of the ports on the Sea of Fallen Stars, or neighboring lands. Not far away Waterdeep. Humans are described as out pacing even the orcs in their growth, and the elves don't always see that as a good thing (part of the reason for the Retreat).
But regardless of that - how far into the Americas did Europeans travel in the first 100 years after Columbus? How many Europeans traveled to the Middle East (other than Crusaders) or China in the Dark Ages? Or Africa? India, perhaps? And when Europeans did start visiting other location in sizeable numbers, what was their general approach? For individuals and small groups, it was usually a religious pilgrimage. Or missionaries, which adds the intent to convert the natives to our way of thinking. When war proved expensive or impractical, colonization. Make them like us, or kill them.
Among civilizations in times of peace, aside from pilgrimages, merchants were the primary travelers. They would come to a new land, and yes, the merchants of Tymanther would also travel (once again because we have a humanized society with money using the same gold standard and they speak the same 'common' even though they are from different worlds). Land caravans find what? Chessenta, great regions of desolation and destruction, and Thay. Trade by ship would also be very likely, assuming they build ships. Pilgrimages don't exist, because they dragonborn don't worship any deities, nor do they have any holy sites in Toril, even if they did.
Cultural, religious and language barriers are huge in societies. More so among different races. Because of Chessenta's worship of Tchazzar it makes sense that they would treat the dragonborn a certain way, but other sources indicate Chessenta is on the brink of war with Tymanther. In addition, the Cult of the Dragon has actively recruited them, which means that as they spread slowly throughout Toril, many people's first interaction with them would be based on that.
Aside from all of that, like the majority of the changes made by the 4th edition, Tymanther is largely gone at this point, with Unther's return. Unlike many of the other changes back (like the Sea of Fallen Stars returning to it's old borders and the removal of the huge chasm to the southwest of Tymanther), Unther returned and is at war with what's left of Tymanther, driving it to small holdings that remain. To me, this seems like they did it in a way to allow the dragonborn to remain for those that liked them in their campaigns, and a way for those that didn't to continue to ignore them since they are no longer a potential major player in the published Realms. As I mentioned before, the Saurials existed in two novels, and promptly disappeared. They were added to Malatra, the RPGA's Living Jungle campaign, but have basically disappeared.
I get that dragonborn are more popular, though, and I accept that WotC needs to provide a story line to allow dragonborn characters in the Realms, particularly since they had already added them. So they can't eliminate them altogether, since there will be players in public adventures that want to play them. And I also understand that my view of the history of the Realms isn't the same that everybody else shares. We all have different likes/dislikes, and when we first come to the Realms has a big impact as well. My Realms is much closer to what I imagine Ed Greenwood's Realms are like, and Elminster's Forgotten Realms bears that out quite well. It's a shared world, and I'm fine with the majority of what's been written, and I love having other writers providing stories of the world because it helps it to be a more living world to me. In a home-grown world I'd have to make everything up myself, and it wouldn't have the same impact for me. But that doesn't mean that I have to like or use everything they publish.
Ilbranteloth
