I always just refer to it as "that boring third world country sport" anytime some enthusiast pipes up about it being "the most popular sport in the world" and then proceed to inform them that it's only remotely possible to refer to it as that because it's the only damn sport in half those aforementioned third world countries since all you need is a ball and space to play it... Usually at this point one (or more) of them will make some comment about it being so popular in Europe and I will proudly announce "I rest my case" and watch their eyeballs try to pop out of their heads. (Especially useful against Italians and Greeks BTW)
Last time I checked Catalunya is not a third-world country. Italy, yes. Spain, maybe, but not Catalunya and definitely not Barcelona.
My general opinion about Americans typically disliking soccer is it's both a fair and unfair assessment. The only soccer America is exposed to is the World Cup, namely because of the worldwide scale of the competition. By the same token, the World Cup is marred by a lot of rubbish soccer. There's a lot of holding, not too much going forward, and everyone's playing for a result with the short lead because it's a tournament (so as to not expend as little energy as possible). The last one in '06 had so much diving and bad fouls, in particular. What's more is, even if your country picks the very best selection, odds are the players aren't used to playing on the same team as each other. Think of it like USA basketball's dream team for the Olympics in the adjustments needed for Kobe, Wade, and Lebron to play on the same floor. The learning curve to make such adjustments is steeper in soccer because timing is more important than individual play to make something happen. Put it all together and you're not likely to see a very smooth game. Now, if I were judging the sport for the very first time, I'd believe soccer absolutely sucks. Add that experience to the prevailing stereotype that soccer is boring and you're likely not going to watch it until inevitably the next World Cup pops around where America once again checks the game out of curiosity.
By the same token, it's unfair to rule out soccer being boring when the World Cup is just the tip of the iceberg. I'm a club over country man myself and I'll say the leagues are far more important and better to watch. For example, if you see the Premiership (England) and La Liga (Spain), the game moves at a more fluid, breakneck pace, and often times, a number of the teams are intent on attacking than just sitting back and soaking up pressure. The World Cup or international soccer doesn't hold a candle to the quality of the leagues or in the continental competitions (UEFA Champions League, Copa Libertadores). Not all teams play boring soccer and I'm glad to say Barcelona and Manchester United have the attacking style down to a T. It also helps if you travel abroad during the highlights of the soccer season. I've had friends who didn't know what this other football was until they sat down in a crowded bar somewhere in England or Spain, showing the local team's games. They love the fan passion and atmosphere, and some become fans of a sport they never envisioned ever watching.
As for soccer being a "third-world" sport...the reason why it's a national sport in the poorer countries is because it was an imported game that's taken hold for many decades. For example, Argentina has the 2nd-oldest professional soccer league, second to England because many European immigrants imported the game when they settled there, especially Italians (why do you think many Argentinians have Italian-sounding surnames). Such was the case in Brazil, Mexico, and India (though cricket is by and large more popular there than soccer).