Nairobi, Sept. 7 -- When the world's largest issuer of the reserve currency begins using debt-management strategies long associated with frontier markets, it signals a shift that global investors cannot ignore. The line between developed economies and emerging markets is becoming less distinct as fiscal pressures reshape government borrowing.

For years, economic vulnerability was viewed largely as a problem for developing countries. Yet the same structural forces that have driven debt management across Africa are now influencing policy inside the US Treasury.

The clearest sign came as US national debt surpassed $40 trillion, dwarfing Kenya's public debt of about $100 billion (Sh13 trillion) by more than 400 times. At the same time, risi...