Governments don't "borrow and spend". Money is a political abstraction, not a tangible one. It is physically impossible for a government to run out of fiat money.

The only things a government can run out of are faith in the future and internal and external trust. When either or both of those disappear, human animals panic and the economy stops working.

Private enclosure of capital - which is equivalent to private enclosure of political and economic power - is far more likely to create that sort of breakdown than high taxes and generous public spending. (Effective - non-corrupt - public spending being equivalent to policy decisions that broaden and diffuse political power rather than concentrating it.)

Effective generous public spending is actually a political negative feedback mechanism that damps wild oscillations in confidence, seeds future investment, and enhances political stability.