1. Trump doesn't care if he costs U.S. taxpayers money. He'd only care if he was personally sued.

2. A foreign party using U.S. courts to sue the U.S. government has always been a dicey proposition. Some parties are more "equal" than others under U.S. law.

3. The current U.S. regime is petty enough to slap retaliatory tariff's on all of Japan (thereby making Americans pay extra for Japanese goods).

Really, there are no carrots or sticks that work on Trump right now. Americans have not yet had their Magna Carta moment.