You are going to be disappointed which is a good thing as the impending doom you think is coming will not happen. Interest rates are raised and lowered to influence borrowing and investment and manage the value of our currency. At times of economic hardship and high unemployment rates are lowered. At times of high inflation they are raised.
it is only a minor part of what interest rate defines or influences.
in your situation of giant overdentedness the most important effect of the interest rate is, as you said, but without proper elaboration - to influence borrowing.
there is certain limit, a % of income/profit that a borrower can spend on debt and interest payments.
as I descrived above, you may pay the same sum having 10 times bigger debt if the interest rate is 10 times smaller.
exactly this way Central bank can reduce or promote business activity - via regulation of amount of money one has at his disposal after he pays debt and interest. - what you mention.
but when your debt is giant the issue is not about extra investment, bit about survival.
for example, let us see how much insolvent the United States of Ametica is.
for the year 2021
receipts 3,581 trillion
outlays - 7,249 trillion
deficite - 3,669 trillion
Deficite is bigger than receipts, obviously the US is an absolute bankrupt in principle, if it loses ability to finance this deficite.
The US lost its ability to finance its deficite borrowing in the market, the Fed has to print money and to borrow it to the Treasury.
This can go on only until Dollar is the World trade and reserve currency and you can trow off this excess of dollars to the rest of the World, otherwise these, dollars would have created hyperinflation already, like in Zimbabwe or Venezuela.
And since China becomes the biggest World economy in 2027, since it introduced digital Yuan in 2021 - within next several years the US Dollar will lose its World currency ststus. The US will lose ability to finance all kinds of debt just printing money...
though, it's sidestepping..
Now, In November 2021, the public debt of the United States was around 28,91 trillion US dollars.
I don't want to spend timd to find out exact composition of US public debt by terms, let us consider it to be all 7 years Treasury notes, the yild is around 1,5%.
So, if the interest rate grows by just 1 per cent, it adds 28,91 :100 x 1 = 290 billion dollars a year of extra outlays.
to curb inflation the Fed has to raise the interest rate to at least 8% ( now, next month inflation will be higher, by March it will be not less than 10%).
Let us consider the hyke to reach 11,5% (so, US government to pay extra 10% on debt) .
If the Fed is serious about curbing inflation the US government will have to spend about 2,9 trillion dollars more to pay just the interest rate!!!!
to remind,
receipts 3,581 trillion
outlays - 7,249 trillion (+2,9 trln)
deficite - 3,669 trillion (+2,9 = 6,57 trln)
deficite will be 184 % of US receipts.
The US is as a bankrupt as Zimbabwe. Fundamentally and indisputably. If the US hykes the rate the Fed has to print another 2,9 trln dollars accelerating inflation despite it hyked the rate just to finance the budget deficite. And most US economy will go bankrupt.
If it doesn't hyke the rate inflation will keep accelerating...
And all American business and households have the same situation.
Do you understand now to what an abyss the US economy is heading?