- each country will impose equivalent taxes on the import of US goods - this is not only expected, but the norm under international trade law. - with the rest of the world, still having free trade agreements between them, will start trading around the US, the US won't be able to compete
The value of the US$ will likely drop by the value of the tariffs. If everyone starts trading around the US we'll probably lose the US$ as a standard currency to trade in, maybe switching to yuan or euros, the US$ is buoyed by it being the currency everyone uses, that's going to drive it even lower.