Realistically you can never expect updates from any non-nexus android phones. If you don't want an iphone (like me) and you want a phone that will get regular updates you have to get a nexus (or pixel now).
But is Xiaomi available in the US and what is version is their is based on?
I haven't seen an authorized seller for Xiaomi and I was under the impression that they are still using marshmallow or earlier. Also all their phones are 4.5"+ which is much larger than the comparably compact SE.
I'd love to get a xiaomi phone (esp. based on the price and alleged build quality) but it's just not worth the tradeoffs.
Xiaomi can be used in the US if you get it shipped over, but it's hard to find the right band coverage for the best experience.
I found that despite not always being on the latest version of Android, they had enough polish and stability on their OS to make it worth being a version behind. I used their ROMs back before they made hardware, and if there was ever a bug, it was usually fixed within a week (or at least acknowledged).
And I agree, I'd love for Xiaomi to sell phones, but like everyone else is stating, the iPhone SE is arguably one of the best compact phones. I hope to have mine for many years.
A very happy xiaomi note 4 user here; have switched from nexus (after battery on three nexus phones in my family became unsuable 2 hours of charge ...); I thought I'd miss nexus more; but xiaomi has been great.
One plus 3 owner here. Received nougat back in December and 3 additional updates since. For a fairly cheap phone I'm surprised with their commitment to software updates.
they also had the OnePlus X which was OPO hardware crammed into a smaller form factor. I would have loved to migrate from my OPO to that but alas they don't make the X anymore.