I launched initially in US & Canada, was planning to rollout to other countries after.
However, I’m not an app developer and because you are far from alone, I always wondered why it is useful to limit your audience to US only?
You just presented your app to a bunch of people who can’t see it and who will never bother to give it a second look. In other words, you’re losing a significant number of potential customers for no gain. Those people will in turn not upvote this submission, further restricting your reach even to those who can use it.
Waiting for doing localisation before launching to other countries is the first big mistake. The second is, as long as you’re restricting the audience, not having a website where other people can see the app to give them a reason to check back later.