The discussion of inflation and wars is just fantasy. Everybody in the world using BTC isn't going to end standing armies.
Payments with BTC certainly isn't competitive. But that probably won't last.
Maybe we'll still need branches. Not everybody can deal with the security required for crypto and there will probably be companies that help people treat it like a regular bank.
Inflation is a real issue and Hitler came to power after the hyperinflation in the Weimar republic. Fiat made that possible.
But Germany still would have had to pay the WW1 reparations somehow. With very high taxation probably.
But the hyperinflation happens after multiple years of expanding the currency too much, often with little impact for several years. That can destroy confidence in government in a way that consistently high but stable taxation might not.
Hyperinflation is not the result of monetary policy. Hyperinflation is the result of near total collapse of systems. BTC is absolutely not immune to hyperinflation. That's just what happens when the price of some currency tanks rapidly as people lose all trust in its stability. The mining cap does not prevent the collapse of BTC as a currency or the collapse of states that use it. Not even a little.
Does a stable supply of a currency, coupled with collapsed systems, create hyperinflation?
Does a currency's value only drop up where systems collapse and not suffer hyperinflation elsewhere where systems are working?