Smart watch leaders are apple and samsung.
Samsung isn't in the big three. Xiami is number one, Apple number two. Xiami is the largest wearables maker in the world. So big that they don't just make their own processors with their own fab, but they use their own architecture!
And they are sold everywhere but the US (or at least I've never seen that brand at any retail location I've been to)
They are definitely sold in the US. We buy them here (they are cheap and resilient.) I don't see them in stores too often, but like on Amazon and stuff they are just a normal item, not imported specially or anything. They are widely available. I like them for travelers because they are cheaper than average, but work well and have the best battery lives (often 1.5 months on a charge!) So you aren't likely to get it stolen, or have charging issues, and if they break just buy another.