OP's comment is interesting, I wonder if many others out there feel the same way?
The Apple Watch analogy itself is flawed, but not for the obvious reason. The entire smart watch industry is a classic example of trying to sell a solution for which no problem exists. It's a throwback to the days before everyone carried around a mobile device, and is trapped between the worlds of the shrinking UI, and our current state which is predominantly visual by necessity.
Voice is a whole nother thing altogether, and regardless of how Google Home, or Apple's offerings go, I think there's a market for everyone dependent on whose ecosystem you prefer to play in, much like the smartphone industry.
What Amazon have done very well is they have as others have already mentioned, created a strong developer ecosystem. This is baked into the product and terminology they use, "skills" tells us that the device itself is never intended to be the end state for functionality, rather it's a platform that can be taught and become something its creators may never have dreamed of.
It's a very smart move, and they've aligned it with the technologies of choice for startups and hackers everywhere.
It's an odd move to keep it US only until now, but it's allowed them to test and refine, as well as grow the developer base. Until Google releases Home, or Apple make their play there is no reason to market it outside the US, particularly in areas where Amazon has little presence.
As for the Echo Dot, it's typically bought by those who have an Echo as a companion for another room. If you want a decent speaker, you don't buy the Dot.