there is significant chance apple will not exist or default in the next 30 years maybe up to 50% there is 99% chance USA will exist and 0% will default
Risk and return for everyone. except those in Congress , the President and his family and friends and everyone else with inside information, are always directly related, but the relationship may not be linear.
The question should really be: why does Apple Corporate Paper yield 78 basis points above US Sovereign paper? Has there ever been a failed US Treasury debt auction, even at these yields? http://cbonds.com/emissions/issue/53013 Does Apple issuing massive amounts of Corporate paper in order to buy back shares instead of investing in their product line research & development make them more susceptible to problems and downgrades in the future? https://www.fool.com/investing/2020/05/05/apple-sells-85-billion-in-bonds-to-fuel-share-buyb.aspx
As a binary question/answer, Apple (private) debt is preferred over government (public) debt. Govt can change any facet(s) of it's debt or it's terms including expiry at any time. (look at what is being proposed in the EU, Perpetual Debt, it never gets paid back, nor does it ever extinguish!).
The US can print money, Apple cannot. Having said this Apple or MSFT are too extremely strong stocks. I voted the US, still because of the fact of the FED. The fiscal situation of a company can change in a hundred years, just look at the few. Amoco, Bethlehem Steel, Compaq, etc. Just think of a hypothetical - you own APPL stocks and preferred and bonds and China and the US enter into a low level, non-nuclear conflict (just to test out the latest toys they have). Do you think this is impossible or improbable? I do not! What do you think would happen to Apple's supply line and earnings?