Remember, these people are here working with little qualifications and making much less than someone more privileged does. I see this as a fault of the capitalists who employ them. Because illegals are paid less, more of them are eligible for food stamps. Everybody in the country contributes to the funding of your welfare state, but the rich "job creators" are reaping the profit. Don't blame the illegals - they've suffered much already and are willing to continue working. Instead blame those who can only gain by providing lower wages and less benefits. If you're upset about illegals and at the government, that's exactly what the privileged class would want from you so they can continue using cheap labour at your expense.
Socialist rant over, now let's get to the foreign politics. Perceptions of Mexico as a poor, backwards country can only be caused by your media. In fact, Mexico is one of the Next 11 economies having grown 3.9% in 2012 vs. the US only having grown 2.2%. While the Mexican GDP per capita is 17% of the US, that ratio will grow to be 48% in 40 years. Even though it's poor when compared to the US, the country is quite wealthy in comparison to the rest of the world and will continue to grow quickly.
As for the rest of the world, I'm not too sure because I don't even know what perspective to take. How do you define what's in the American interest? Is the US not taking a more direct action in Libya and Syria a sign of it being unable to act like it once could, or that it's smartened up and learned how to achieve its goals without intervening directly (not so much in Syria, but still). And is the US pivot to Asia going to lead to more cooperation or suspicion with China? Now I can say for sure that industrializing countries want to usher in a multipolar world where US influence will not be paramount - it'll still be powerful and have friends, but won't be calling the shots like it could post-1990, or even during the Cold War. So you could even frame the question like so: the US will be intervening too much with respect to how much regional powers want sovereignty in their spheres of influence (Europe, Russia, China, Brazil, Iran - among many others).
Quoting simply because this in a nut shell. I mean you really cannot summarize it better than this. Only thing I can add as I don't really see it mentioned if it is not hinted at: They are not "stealing" our jobs. They are taking the jobs we DO NOT WANT TO WORK. They have the last job we'd ever take if our lively hoods depended on it. I saw some crack about them only working in select restaurants. As Ironic as it is the only two types of restaraunts I've seen a majority of Mexican workers in is Taco Bell and Mexican theme'd. Everywhere else in my state is either Black or Asian decent. In the five cities near me the Asian cuisine has gone up by a large margin. Many new Asian themed restaurants pop up every other month.
We do need to focus more on close to home issues rather than putting out noses into everyone else's affairs, but I wouldn't say we are too involved. A lot of the "illegals stole my/our job(s)" is grossly over exaggerated. I also have seen friends deported because their parents didn't have green cards after 5 years. The ones who parents did get green cards are paying taxes and living happily while their kids go to college to get better careers.