Yes, but if everyone does that all the time then there's zero cross-border capital or investment flows which means... you've solved the problem?

Every country will have zero current account deficit which is getting you a long way towards what people are trying to achieve with tariffs. You could still have a trade deficit because of foreign investment income, but nothing like the massive imbalances that are seen today.

Just mathematically, the only way you can balance a huge trade deficit is with an equally huge financial account surplus. There is no way for everything to be made outside the US and bought by people inside the US indefinitely with no cross-border financial flows.

What you’re talking about is something like a hawala system, which works but it will only work indefinitely if flows in both directions are balanced, otherwise at some point you will have to move money to settle up