You ask a lot of questions, which is good, but, maybe you should try reading some books(oh god - i sound like my mother, lol) In my opinion, no american carrier i have flone internationally, (united, and pan am) is up to the same standard as others. I know americans hate to hear it, and i am not trying to snob them, its just that outside the US, people never say anything great about american carriers. This is basically to do with the culture of aviation in other places. Here in australia, we have two world class domestic carriers. I mean, you name, you get it domestically. Everything except alcohol is served complements of Ansett and Qantas. And its great to be able to fly like this, however, by world standards, its very expensive, especially by US standards. The same goes in most of asia, where for short haul 2 hours flights you will find yourself onboard 747-400s or 777s or A330s/A340s. There is no discount carriers about. I have to say, as much i love being pampered, is it really worth it just for 1 or 2 hours? Long haul, yes, i demand it, but i think we'll all live fine for an hour or two. So, is what happans is some carrier like southwest comes along and makes this a reality. fares drop big time. The others still try to maintain their full service image, but, they can't because as much as a lot of people like those little extras, they chose not to spend the money for what ever reason. So, then, the full service carriers really can no longer offer full service in order to stay profitable, as they had to discound to avoid loosing about 90% of their customers on challenged routes. So, full service becomes crappy service made out to be full service. Now, in the usa, this culture has sort of spilled over into international operations. that is, the full service not really delivering. Except there really are not any discount international carriers - there are fare to many international bilateral agreements between countrys and life isn't all that easy for such carriers on those routes. Its far easier to make a small profit on each passenger a few times a day then fly them all half way across the world. and your markets bigger - far more people can afford $100 than $1500. Not even mentioning the time factor - people can afford a day or 2 away in many cases, and not a second longer. So discount carriers tend to stay away from international routes.
Anyway, on international routes, US major carriers are staffed by people who have been trained, educated and have their expirence in this environment i talked about. The trouble is, their competitors are not. Avaition in Europe Asia and the South pacific is a different story. Basically, because long haul really is a long time and those little extras to make a big difference. So, when these carriers fly to the US, they do the same thing they would do everywhere else. The result is carriers like British Airways making a killing on they're US routes. And, a very important foreign market not being very impressed with US carriers. As my travel adjent says "nobody ever says anything great about American carriers - nothing to write home about". In a lot of these markets, the foriegn customers have higher living standards and more disposible imcome than the average American. I know this for certain, having lived in Great Britain, Germany and Australia. This means, a lot of the travelers onboard are not american, and thus not accustom to the american aviation culture. The prices on contested routes are generally very similar. And, these people are not satisfied with the product, where many americans would expect little more.
Having more disposiable income means, that in many cases, the any carrier is chasing after that market more than the others - they simply can afford to pay. I only have to look at flights to Australia from the US - its much cheaper than buying a return ticket from australia. ie syd-lax-syd is a lot more expensive than lax-syd-lax. On japanese routes, its not uncommon for the price to be literally thousands of dollars higher. So, when they get on board a US carrier, and the service is less than what they are used to, they are not satisfied. The US carriers, believe, since this is they're culture, that what they give IS full service, because its a little better than they're domestic product. But as somebody else once pointed out to me, BA's shuttle is better than certain US carriers internation economy class.
So, to answer the question, the service on american carriers international service is good for americans, (those not used to traveling on foreign carriers - i have seen many americans complain about it too that are used to traveling on certain foreign carriers) but, you do have a choice, and, if it were me, i would avoid using an american carrier for international long haul flights. Now, i always give Qantas a hard time, but, my last flight to the US was Syd-SFO-Syd in febuary, and it was UAL. I do wish that i had used Qantas to LAX instead now, looking back. If you get a substancially lower price, go on the us carrier, but, if you don't, let yourself be pampered a tad more, and fly a Europian carrier or an asian or South Pacific carrier. The favourites are well known and obvious - just look out for the ones who have won the most accolaides, and maintain profitablity thoughout they're lives - they is a reason why people keep on comming back to chose these companies, allowing them to stay profitable, or very close to it, even in bad times.