When expressing that poverty is a real issue in the US, my friend responds with "we are far better off than third-world countries." Is this a fallacy?

I would argue that, on first glance, it appears to be, and it falls under Relative Privation . The fallacy is in the comparison of an unfair worst-case scenario (third-world country poverty) to our case (poverty in the US). You are clearly stating that poverty is a problem, and your friend appears to be minimizing the importance of that problem by comparing it to something extreme. Your friend's comparison does not negate your claim that poverty is a real issue (implied importance).

In fairness to your friend, what he or she said was factually correct, but facts alone don't excuse one of fallacious reasoning. If your friend's intent was NOT to dismiss your claim that poverty in the US was a real issue, then it could be argued that his or her comment was not fallacious, but rather made to put the problem in perspective (globally) or perhaps even the intent of your friend is to call your attention to the larger problem of poverty in third-world countries.

The bottom line is you cannot know the intent of others unless you refrain from calling "fallacy" and keep a dialog open. Give the other person the chance to explain what they mean. Then, if the fallacy is clear, go ahead and call "fallacy" :)