Where did I say anything about Japan carrying the Switch 2? I just mentioned how popular Kirby is worldwide, and it is a giant in Japan. Which is why they prioritized it, especially considering the state of the game compared to Prime 4. Sure, in today's age of gaming, you need to appeal worldwide, which is what Nintendo does.
It's not a surprise that the Switch 2 had a decline in sales in the holidays since most people who were going to buy it bought it at launch. Or even when the recent Legends game came out. What else did Nintendo have that really got people to want to buy the new console if they didn't already, considering there aren't stock issues? Nintendo will more than likely be fine, but they do need to announce new games within the next few months since right now they haven't announced their big 2026 holiday release, with the next-gen Pokémon coming out in Nov 2027 most likely.
Even taking that into account, Air Riders did better than expected in the US, which was a major contribution to selling less than a million outside of Japan. For a racing spinoff for a series that hasn't had an entry in 22 years, that is a solid success for them.