Gads, don’t scare the socks off them! It’s not that bad.
I always buy travel insurance when I buy my ticket for a foreign trip, because that means you’ll have some medical coverage abroad. Medicare doesn’t cover it, although some advantage plans do. It also means that, if worse comes to worst, they’ll bring your body back (an expensive process).
As for the luggage, it’s always a good idea to travel light, but the best thing to do is to have essentials in a carry on and then pack lesser used things like heavier clothing, bathing suits, etc. In a bigger bag. Luggage doesn’t get lost that often anymore, but it does happen, and while you usually get it back within a couple of days, you might want your PJs before then!
Also you can always buy stuff...this is not up the Zambezi and they have all the American and European chain stores (and even discount stores!) there. Most people who deal with tourists speak at least some English, and many speak it very well.
And believe me, the US government already knows you’re there...probably because they’re afraid you’re evading taxes or something!
I can pack everything in a backpack regardless of the trip length. The key is taking clothes that dry quickly, you won’t need to bring so many clothes. I literally wash the clothes when I take a shower and use the excess shampoo as detergent.