> I thought one of the Aleutian Islands in Alaska extended east of the International Dateline, thus making Alaska the easternmost point in the U.S.

Unlike north and south, which have the equator as a reference, east and west are always relative to something else. (That wan't very clear, I know.) The Prime Meridian is just a convenience, and could just as easily have been defined anywhere in the world, there's nothing about it that makes everything on one side fundamentaly "east" and everything on the other side fundamentaly "west". IMHO, the way to decide whether point A is east or west of point B is probably:

1) Measure the distance from B to A when starting at B and travelling east.
2) Measure the distance from B to A when starting at B and travelling west.
3) If distance 1) is shorter than distance 2), A is east of B.
4) If distance 2) is shorter than distance 1), A is west of B.
5) If distance 1) and distance 2) are the same, then A is neither east not west of B.