The short answer to this question is no. With very limited exceptions podcasting apps do not support the ability to restrict your podcast to certain geographies.
One notable exception to this rule is for podcasts that appear on Spotify. Megaphone has a custom ability to add a <media:restriction> tag to your RSS feed that will restrict your podcast to a specific country in Spotify. If you're interested in doing this you can make a request with to the Megaphone Support team. Please give at least 2 weeks notice. Again, Spotify is the only platform that honors such restrictions in the RSS feeds.
Users can also reach out to Apple about restricting your podcast to certain countries on their back-end that will affect iTunes and Apple Podcasts. Megaphone doesn't have anything to do with this - this is entirely handled by Apple.
Advertisements, on the other hand, can be geotargeted during setup in the Campaigns section of Megaphone.