[XFrequentist]

"Living in a very sanitary environment like the US can (potentially) weaken your immune system."

There are lots of vague hypotheses like this floating about, but IMHO[1] they're pretty flimsy. The fact that you don't have immunity to various foreign bugs doesn't imply (at all) that your immune system is "weak".

There's better evidence that sanitary conditions could increase allergy, which is an overactive immune system, not a weakened one.

Pollution, which you mention later in your comment, has nothing at all to do with immunity.

All that aside: boil it, peel it, cook it, or forget it!

[1] - Also not a doctor, but I am an epidemiologist.

[Ixiaus]

This is purely anecdotal and may also be related to the two-page long list of vaccinations I received, but I've rarely ever been sick since being back from India (where I did get sick a few times, pretty badly) and when I am sick, it's usually something very mild I get over within a day or two.