So, how high are the "inherent risks" in your country? How do Moody's Fitch, and S&P rate your government's debt? If they view it as investment grade, I wouldn't worry too much about default. If they characterize it as less than investment grade, I would be very cautious. Being denominated in dollars protects you against exchange rate losses (at the expense of losing the upside if the dollar declines against your currency). BTW, the fact that the government is offering a dollar bond indicates that at least some investors are concerned about exchange rate risks. How much is the difference between the interest rates of the Government's dollar and local currency bonds? The difference should tell you something about how other investors measure that exchange rate risk.
The real risk is that inflation overtakes that 7.45% interest rate over the next 20 years. Of course, buying bonds might be particularly profitable if you are a contrarian and believe that inflation will be tamed and interest rates will be dropping. That said, with a historical average of 6% inflation in your country and the global economy potentially entering an inflationary period, 7.45% doesn't seem compelling to me.
I have no opinion on VTI. A lot would depend on your specific circumstances and what the rest of your portfolio looks like, but I would question buying stocks if you really need this money to produce "consistent cash flow" as you stated in the original post. Personally, if I were in your shoes and needed to rely on cash flow from this investment, I would be looking for alternatives beyond US/global stock markets and a long-term bond. Maybe rental real estate, for example, but that will be dependent on your specific market.