Why impossible? We could reach a point where interest payments exceed all other government spending combined, healthcare and education will be shit, but im confident the government can get it done. We could have the majority, why not all tax revenue go to servicing the debt? The streets will be filled with roving criminal gangs and you wont have electricity at home, but theyll just blame it on the rich and corporations as always. We could exceed total tax revenue in servicing debt, thats a goal to aspire too, they can issue an unlimited number of bonds to make payments on bond debt. What, you think you can escape? The banks have to buy their bonds, the central bank will buy the bonds for yield curve control, the roads will be gravel and the water will be sewage, but its all in the name of protecting the economy.