That's not really how it works. For them to spread things around like that by limiting US price rises would likely mean selling at a loss in the US. It doesn't matter how big the US market is - selling at a loss is not something that will happen (and a bigger market is worse in those terms). If US tariffs really do come in and really do hit GPUs (neither of which is really a given), then prices will increase in the US. At some point, price elasticity will start to limit demand there, which will mean more cards being shipped to the rest of the world. Nvidia could try increasing prices in the rest of the world to offset lost revenue from the US, but those same price elasticities will still applies elsewhere in the world.
Edit: What you need to remember here is that it is reasonable to assume that Nvidia is already pricing globally at the point it thinks will maximise profit. If US tariffs mean it can no longer do that in the US, it's going to make things worse for Nvidia if they throw off the balance in the rest of the world as well.