Keep in mind that relative to your home currency you are invested in US Dollars, so you already have risk/opportunity there. The dollar could rise or fall vs your home currency during your stay here. US dollar inflation is at 2%, and CDs or other safe investments can be found yielding 1%. If you're seeing CDs or other safe investments in your home country earning something like 8%, it might be because their currency is expected to experience 9% inflation.
I'm curious about the taxation issue, is it that you don't want to complicate your US taxes with foreign investments? If not, what changes the tax situation when you eventually move your money back to your home country?
I would suggest you repay debt either here or in your home country as that would be the safest bet, unless this is strategic money like a security fund.