The FED buys the debt with newly created dollars. This is inflationary, but because they stopped reporting M3, we really don’t know how much of this goes on. When the FED buys debt with new dollars, almost everyone is happy. The debt is paid, the fed get the interest, the only losers are holders of old dollars.
The value of the dollar vs the euro has been dropping about 10% per year since 2002. Those who hold dollar debt at 5% are losing 10% on the exchange rate each year for a net loss of 5%. I wonder how long people will keep lending us money at a loss.