I would disagree with this. Indebtedness was enough to drive the European conquest of the Americas from a pretty early point.
Indebtedness early as a driver, how so?
If you mean the crown of Castile, conquest happened before Philip II really got into his ruinous wars in Flanders. The crown went bankrupt
long after that and
despite the american silver. It's some 50 years. If anything the early flow of gold from the conquest of the Aztec and Inca empires, and later silver, destabilized both businesses and tax collection across Charles V's and later Philips' territories.
Philip's strategy in the low countries as religious strife engulfed those regions would necessarily have been different if he didn't had the income from the treasure fleets. The role of genoese bankers providing gold to pay the armies in the north against the fleet's silver from the south simply wouldn't have been possible. Hence the need to substitute collections from tax farmers for the silver (leading to mounting debt and defaults) when the fleets didn't provide enough would not have happened.
I can agree that the wars tied to the Hapsburg attempt at
universal monarchy did drive the financing of further conquest in Central and South America, after the spectacular pillage gotten from the Aztec and Inca Empires. The lure of gold as I said. But North America, that one didn't attract attention. Past the "civilized areas" of the great empires there wasn't relevant loot to be had.
Imo the conquest of the American empires drove international banking, larger scale warfare and state indebtedness in Europe, not the opposite. I guess I'm ending up agreeing at least in part with Lenin's thesis of imperialism having been indispensible for capitalism, albeit at an earlier state than he was focusing on. The modern instruments of state debt were first used oon a large scale by Philiph II and his italian bankers. The dutch and later the English were immitators.