After hypothetical successful debt relinquish negotiations, any new US debt would have similar interest rate to Argentinian debt, 30% or so. Wall Street would shrink and London (or Frankfurt) would become new global financial center.

In reality, countries do just as what they do now. They raise counter-tariffs. The US faces coutertariffs from everyone. Other countries only from the US. Trade between countries other increase and they gradually adjust. Europeans start buying less iPhones and buy more Androids made in South Korea. Less Fords more Nissan.