Running up debt is way less important than a country’s ability to keep making payments on that debt. In a smaller country than the US, a country could default on its debt, and creditors could impose almost any conditions they want on additional loans (see: Greece). Even without default, the risk of default can make lenders wary of investing, and require higher interest rates to loan the government money. This means more money going to interest payments rather than things the government would like to spend on.
The US specifically is the world’s largest economy and there’s 0 worry that our government will stop making making payments on its debt. So, no one serious worries about catastrophic consequences from our deficit. We’re paying about $500 billion in interest yearly on our debt, which is about 2% of GDP, but a lot (most?) of this is paid to American buyers of govermnent bonds, so it’s not like that money is leaving the country entirely. It’s just not very socially efficient way to spend $500 billion, lol
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