Companies release features to some regions all the time. For example, in Google Photos, you can search by face in the USA but not Europe (due to differing privacy expectations).
That sucks; glad I'm in the US because I use that feature often. It's great for when friends ask for the photos I took of them.
In any case, I predict the Steam situation will differ because privacy and retail goods are valued differently. Americans are going to want that feature if Steam has to implement it, and they have options regarding what game store they use; it becomes a point of competitive advantage for Steam to switch it on in the States. They'll have to do the calculus on whether they lose more potential developers if they do vs. lose more potential store users if they don't.
Funny enough, if you use a USA based VPN server, the option will appear on your account and you'll be able to activate it. It Will stay activr for your account even if you switch back from VPN
That's deliberate... Those kind of "annoy the customer" limitations are all for PR/legal/business reasons, and the engineers building the features want to make the restrictions as easy to get around as possible.
