Hi there,based on my experience, you can launch your app in many countries at the same time. Just as Matthew Campbell mentioned, you should do good app localization before launch.
App localization is the process of adapting your app to a particular language and culture, it has huge positive impact on your app visibility in app stores. Most people prefer to find and install apps in their native language.
When you localize your app, what you should remember is that app localization is not a translation of an app, translation being a small part of the entire process. It’s about language, culture and other geographic references. You should take legal requirements, currency, numeric, date and time formats, icons, symbols, colors, graphics or ideas that in a culture can be misinterpreted into consideration.