Hmm..lots of opinion based POV.."to me"..."im not sure"..."arguably"..etc. Lets deal in core facts, the EPL; a league that is just 21 yrs old (less than half), a league that has seen a revenue increase of $1.6billion in 3 yrs, a league with more foreign billionaires sniffing around teams than any other sport (and quite a few of being yanks from...the nfl), the most watchd sports league on the planet that has sold the tv rights to more territories around the world than any other sport (and by some distance), the EPL has the competition of being just one league among five major leagues in Europe and yet it has already has over half the revenue of the only league of NFL. When you are only reliant on one market the scope for growth is limited, in contrast to the EPL.
As regards socialism/capitalism...both systems in sport are wrong...one rewards failure (yeah..let's lose all our games so we can draft good players) and punishes success...the other rewards big transfer spending (which is why financial fair play is being brought in...% income spent per team). While neither system is right, one of them is trying to get it right.
That's that cleared up.
The question of "right" is neither here nor there; the competitions are simply a reflection of different operational structures, and what the EPL reflects is the grossest of free market capitalist inequalities. So you may argue that the NFL punishes success, but the EPL institutionalises it, in effect creating an unbreachable class divide between the top 4 and the rest. In that sense, as a 'market', the EPL simply offers far less genuine choice. In the NFL, AFL and even NRL you can generally keep the faith that your team's day will come, but as an EPL fan you effectively have to resign yourself to being part of a permanent loser class of supporter if you aren't part of the top four fraternity - or are uncomfortable doing what the majority do and jumping on the bandwagon of a team that couldn't be more dislocated from you if it was on Mars.
What the NFL does in reality when it "punishes success" is ensure the appeal of their product is not retarded toward less than a hand full of major teams, as it is in the EPL. The core difference is that, as you say, the NFL is always trying to find the right balance, whilst the EPL is not.
This is what sets them apart; a business, the NFL is considered one of the best run in the United States, almost always reaching its targets. This is a sobering thought, given that they are currently targeting revenue of $25 billion within the next 13 years. The EPL is clearly successful, but it's core product is far less impressive and more poorly structured.
Lastly, I don't buy that the NFL is limited by the US, as it has shown appeal in surprising places. You talked about the way people came to Melbourne to watch the pommies of the EPL play, yet the NFL has done the same thing: in London last year the NFL had the Jaguars play the 49ers at Wembley and sold it out pretty quick. This, for a foreign sport with teams poms have no association with (though the vast majority of EPL top four fans have zero connecting them with the clubs they support too).
The key failing with league is the poor international set up...get that right and it has a chance..because the club game in cricket, rugby union and rugby league barely register. So given that cricket and Union rely on international game to receive any sort of coverage (and it is in small pockets), it's also the only way league is going to get any. In terms of Ireland, its up to the league governing body if they want to grow their sport by promoting it better, setting up youth programmes (can't ever recall seeing league being played here...just football, Gaelic football, hurling, and Union..in that order). Having an "Irish" team full of Aussies and Yorkshiremen ain't gonna get anyone interested.
Unfortunately, the failure of International League is really the failure of English Rugby League... For New Zealand the main and pretty well only game has been Rugby Union forever, so their presence in League is actually a growth and success story (if they get a second team they will become increasingly formidable at international level, as they already have so many players in the Aussie NRL teams). If England had a stronger and more representative club comp, then the international game would be more sustainable.
So I think you have it the wrong way around; having a strong international scene would help England, but you don't get one unless England are competitive, and they won't be until they fix their club scene. As it is, England simply aren't strong enough, a fact reflected in their inability to beat us in any series since the 1970s.