According to a new report there are 38 countries in total where the feature will be operable. Yes, the US is one of them, though it wasn't as simple as adding the feature and leaving it at that.
Google needed a "special exemption" for Motion Sense on the Pixel 4
Motion Sense is powered by Google's Project Soli chip, which uses radar technology. The radar technology in particular is what called for permission.
In the US specifically Google needed a "special exemption" from the FCC for the Project Soli chip. And, since it acquired that exemption, Motion Sense will work in the US. There are however some countries where it won't work.
This includes Mexico, Japan, India, New Zealand, and possibly Australia. All countries where Google is likely to end up selling the phone. This doesn't mean that the phone itself won't work there. Just that the Motion Sense feature will be inoperable.
That is, unless something changes before the Pixel 4 is released.
Google only needed permission in certain countries
The report states that because of the advanced radar technology, Google needed permission for it to work in "certain" countries. It doesn't say "all" countries where it will work required Google to get special permission to market the tech.
That could mean that Google had an easier time in some countries than others. Perhaps in locations where regulations may have been less strict.
The list of countries where Motion Sense works may not be complete
While 38 countries seems like a pretty large list, it's not when you consider how many countries Google may want to sell its next phone. Motion Sense is a major feature of the device, so it's highly unlikely that Google wouldn't do everything in its power to get it working everywhere the phone is sold.
Considering this, it's possible that the list of countries where the feature will work is incomplete. If that is the case then it could be for any number of reasons. As for the countries where it does work, aside from the US, Motion Sense on the Pixel 4 will work in the US Virgin Islands, as well as the UK.
It will also work in American Samoa, Austria, Belgium, Bulgaria, Canada, Croatia, Cyprus, Czechia, Denmark, Estonia, Finland, France, Germany, Greece, Guam, Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Puerto Rico, Romania, Singapore, Slovakia, Slovenia, Spain, Sweden, Switzerland, and Taiwan.
Google will officially unveil the Pixel 4 at its October 15 event, where it may also announce a few more products. Alongside the new gesture feature, the Pixel 4 is also coming with a more powerful camera setup, and no notch.