Hawaii (except for Midway Island and a few other atolls) lies comfortably well east of the 168 parallel a would not be affected by a dateline splitting the Bering Strait and going straight down.
You're right, Hawaii is not affected by the 168W longitude -- it's when Jerusalem is regarded as the Prime Meridian (line 0 )that Hawaii is affected.
The dateline has nothing to do with the prime meridian being in Greenwich, England.
Only partially right. From Greenwich England (line 0) the longitudes are counted to the 180th, both to the east and to the west. The globe being divided into 360 degrees -- 180 is exactly half way around the world from Greenwich, and thus has become the DEFAULT, though not the actual dateline.
It's when Greenwich England was chosen as the Prime Meridian in 1884, that all this mess in the Pacific started, with some wanting the 180th to be the official dateline.
Yet it was never declared official -- countries in the area were left to chose which side of the date line they would be on.
Had these Islands been left alone, they would all have simply continued to be in the eastern hemisphere where they were in the first place.