It's not that simple. Untold numbers of U.S. bonds are held by people running the "carry trade" (borrowing JPY at low interest rates in order to buy mostly U.S. treasuries and make money on the difference).

If you raise JPY rates, then these U.S. treasuries are going to get liquidated driving up U.S. rates and of course the U.S. doesn't like that.

So, I believe the US is pressuring Japan NOT to raise rates, i.e. to save the U.S.'s own currency.

This is undoubtedly why Bessent bought $5 to $10 billion JPY using Euro awhile back (as rumored, the exact amount is a secret). That way he could try and bailout Japan and by using Euro instead of USD, not affect US inflation so much. He also did it without telling anyone in Europe which quite pissed them off as well.

It's really funny seeing these shenanigans take place with all the pompousness the US shows regarding its currency and how it pretends it itself is not going broke.