The rot is that a empire selling security can subsidize any economic policy indefinitely and is completely decoupled from anything resembling a free market forever.
I would quibble with the "forever" there. Eventually empires have bad leaders, and Trump is showing how a bad leader can disassemble an economic empire in just a few short years. One can do tremendous damage from the inside, especially when the populace has been cowed by broad misinformation and the checks and balances have been removed by single party rule.