system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: The US Treasury has stellar creditworthiness, but it seems to always pay its debts by incurring more debt. So if paying debt with debt is no big deal, then why couldn't Greece do the same thing? Why did they have to default?

I'm an economics major but international finance fries my brain like an egg. Please help me understand.
gpt
Because Greece would be a *state* in the US, and especially in the US Economy.

The US incurs huge amounts of debt, but has the economy to cover its costs.  Basically, the US is a guy who borrows $10million and makes $8million a year... and Greece is the guy who makes $50,000 and owes $2.5million.  

Nobody would lend more money to Greece... they were already wobbling.  The US is a lot stronger of an economy, so people are more than happy to keep throwing money at it.