It does affect whether a Japanese company has a monopoly on the use of the name for a product being marketed in the US. Someone else could market a game called Shenmue in the US now.
Well - that's assuming there's no provision in trademark law that would allow Sega first dibs on the name again if someone else tried to register it, because of their prior use. But I guess Sega would have to sign something that said they would actually use the mark again within a specified period. They can't tie up the name forever if they're not going to use it.
And that someone could be Yu Suzuki.