What happens in a country that has a high debt ratio?

In a country that has a high total debt ratio, one should expect the following : The maximum sustainable interest rate is lower than in an economy with a lower debt ratio. This was clear to see in 2018-2019 in the United States; An expansionary monetary policy is not very effective at boosting activity, since economic agents can hardly run up more debt. This has been visible for example in the euro zone; The effect of growth shocks is amplified by their effect on borrower solvency. This makes the slowdown in global trade and rising oil prices, for example, dangerous.