In response to this answer: The US is not a “third world country.” In fact, “first,” “second” and “third world countries” are outdated terms that the majority of people don’t even know the correct definitions for and grossly misuse.
I think there is an important balance. It is important to prioritize a country’s own people first. However, expecting to fully “fix” all of the country’s problems before engaging with others is unrealistic. We will never fully solve all our problems, and cooperating with other nations actually helps us solve (or improve) some of our issues. So yes, a country’s first priority should be to its own citizens; but, a country can cooperate with others without sacrificing that priority.