As good as US doctors are, they are often completely stumped when it comes to common Third-World diseases. They simply do not expect to find them and have little experience in making a diagnosis.
One thing to remember if you ever travel to exotic locations is to tell your doctor where you have been if you become sick within the next six months or so. If your doctor is confused, see a specialist with experience in tropical diseases.
Somewhat true, for some situations, but they also know enough to do the referral to infectious disease docs.