I think it’s more along the lines of :
“You’re maxxed out - you can only borrow up to the value of your house, $250,000…”
“OK, here’s a new house valuation that puts it at $350,000; please up my credit limit.”
How could that possibly cause a problem?
IANAeconomist but - I think it’s just a trick to get around the limit that congress has imposed. Dollar bills are just “promises to pay”. Coins are considered actual money. If the government creates a trillion-dollar coin it has a trillion dollars more. Put it in a vault and now borrow against it, and technically you are not exceeding your debt limit because your trillion of extra borrowing is balanced by a trillion of cash deposit.
Whether congress should play these games with the debt limit, and whether the Treasury should play these games to get around it - separate debate for GD.
What effect it would have?
Economically, virtually none. All spending still has to be approved by Congress (and the president). So it’s not like suddenly the land will be flooded with milk and honey and money, causing massive inflation and financial armageddon. The economy would go on as normal. One less contentious annual debate would disappear off Congresses obstructionist plate.
Up until Obama became president, raising the debt ceiling was a normal, regular occurrence, a symptom of the fact that Washington collectively could not control the urge to inject its pork-infested veins with a few hundred billion more each year. Somewhere in the paroxysm of shock that the Republicans (a) lost (b) to a black man (c) who did no,t like Clinton, keep mumbling the mantra “restrain spending” until blue in the face (since blue was not an option)… Congress (R) began to obstruct the raising of the debt ceiling to make its point.
Again, the productiveness of the process is GD territory. The fact is, Washington has for decades spent more than it takes in, except for a brief respite under Clinton. It spends about 30% more than it takes in, typically. Getting this in order means either severe unpalatable (to both sides) cuts, or higher taxes, or more likely, both. As the merde approaches the fan these last years, the volume of debate has increased.
So every time there is another impass - a cliff, a ceiling, whatever - people float ideas of various legality and reasonableness that would detour the roadblock.
What would really happen if they did this? Nothing, other than the righteous screaming from congress and the level of vitreol over the administration would hit a new high.