I recently conducted a study on this particular issue concerning the 1500 hour requirement introduced by the FAA and whether other states should follow.
Schnowzer is correct in saying it was certainly a political issue following the colgan air crash. Despite many studies have pointed to the fact that the accumulation of further flight hours in this way has limited value on competence, congress still pushed the ruling.
The US still prefers to adopt a rather old fashioned system of flight training and geared towards gaining flight hours. Other states appear to be more proactive towards more innovative ways to gain competence, such as the MPL. Introducing the 1500 hour rule to other states could also prove to be a problem due to the lack of GA in comparison to the US.
It has been found that flight hours alone can be of limited value, it depends what you do in those hours. For airline operations in particular, more emphasis needs to be placed on training in multi crew scenarios developing both technical & non-technical (CRM) skills in a relevant environment. This also applies to "experienced" pilots with many hours on type, they need to continually train and develop these skills otherwise further hours mean nothing. Studies have shown that pilots from airline cadet schemes with no previous experience have been just as competent as pilots with previous GA or other airline experience.
Despite the larger GA scene in US, the 1500 hour rule is still managing to create a pilot shortage for itself, mainly in the regional carriers. Therefore, it would be prudent for other states not to follow suit.
It is interesting to note, certainly in Europe and many other parts of the world, the traditional route of gaining experience flight instructing, then regional carrier, then major carrier has changed considerably. In fact, the LCC`s have become the first step, then personal choice dictates whether they want to progress to a career airline, i.e either a long haul operator or even some regional carriers that have better terms, conditions, lifestyle, seniority pay scales etc.