How come Irish rugby clubs do so well in Europe compared the English?

BLM, although I agree in principle (England having more clubs Vs Ireland having 4 provinces) the population of both countries is enormously different (ie English should have a much larger number of rugby playing men than Ireland has so thereby the English clubs should have a larger local pool of players even if there feeder areas are smaller).

The English system is built around the clubs. Each is individually owned and operated and their ultimate purpose is to generate profits for the shareholders. The must also be successful on the field, as the possibility of being relegated to a lower level can be financially disasterous -- something demonstrated by the demise of the earlier incarnation of London Scottish in the 1990s. So you have something like two to three dozen professional clubs, all scratching and scrambling to survive.

The Irish system is built around the four provinces. All of the clubs are ultimately intended to feed their most talented players to the professional club representing that province. The success or failure of the individual clubs below that level is an afterthought, at best.

What that means is that while professional rugby in England as a whole is probably stronger, each of the four Pro12 Irish clubs has a broader base to build on. This allows them to stay competitive with the English and French clubs.

Rugby is not too big in the US. We have other useless sports such as Football, Baseball, and Basketball where players get payed millions to throw a ball back and forth on a court or on a field

Well unlike their national team they're actually shịte and at playing dirty to, hence why they're pulling out of the Heineken Cup cause us Irishmen keep kicking their ạrse.