to tl;dr: 300 million vs 30 million.
Not just the US but that would cover the entire western world.
No one has complied exact numbers but from known production and declared customs invoices, at least 20,000 Tubas are made every year. So I'd imagine there's decent enough market for japanese drums outside of Japan.
Love it when they don't make it overcomplicated and make them very understanding of each other. Feels like that's the case for most recent mangas now fortunately, especially when you have Rent a girlfriend...