Setting aside his conflation of appropriations with the debt limit, he's acting like
the Treasury is allowed to prioritize debt payments- that's not how it works: they pay our obligations as they come due
Treasury receipts match their obligations- that's not how it works either: the whole issue is there are timing mismatches between Treasury receipts and payments, even in an environment where we didn't run deficits.
Amash is playing a really stupid game here of speaking of the debt literally and acting like legal obligations can just be reneged on. He's arguing the equivalent of hiring a bunch of people to do work for you and then not paying them. Sure you aren't technically paying them until you actually give them money, but you created an obligation to pay them when they rendered services for you. In this case the government doesn't have cash on hand for that payment, so needs to borrow to make that payment. Borrowing is constrained by the debt limit, but that obligation still exists, so if the debt limit isn't raised that payment is indefinitely delayed until revenue comes in. It is such a literalist and dumb argument.
If we raised the debt limit 500 trillion dollars today we wouldn't suddenly create 500 trillion in debt. The Treasury borrows according to its shortfall based on its existing legal obligations.
This is just basic accrual accounting and it is rich that Amash is acting like everyone else is gaslighting people and not him just to shoehorn his fiscal conservative argument. I don't even know why he feels he has to do this to make his argument. It is somehow an argument fiscal conservatives make all the time without doing this dumbness.
Otherwise it wouldn't be possible to default. The whole reason the US government can default here is because they owe money to people.