Your app is available near world-wide. I don't have the complete list of countries, but it is either an exact mirror or close to an exact mirror of whatever countries Facebook is allowed to operate in.
The decision to localize your app to attract non-English speaking users is yours to make.
To help you decide, you can go to the analytics page for your app from https://dashboard.oculus.com and look at the Usage stats. Change the Breakdown to Country. That automatically shows usage from the Top 5 countries your app is used in.
If you want to see usage stats from a country not in the Top 5, you can type it in manually and add it to the Chart.
BTW, as far as China goes, Oculus does not have a presence there. Samsung has an app store in China, but we know nothing about their app ingestion process. If you want to sell your VR app in China, you'll have to ask Samsung about it.