Theoretically, the argument against tariffs stems from the idea that a market increases the net surplus for everyone involved in the trade. This is because each individual in the economy would be able to focus on their 'comparative advantage' and trade to obtain a larger basket of goods than if they tried to create everything themselves.

The way the US is expected to enjoy this trade surplus (in a world where it is a net importer) is through lower prices for goods. The benefit the US gains from this reduction in prices etc. is meant to on the whole offset the loss in jobs, exports etc that might come from globalism. Whether this happens or not is clearly a moot point.

I believe the issue might be that while the US has enjoyed the surpluses of globalism, it has not redistributed that surplus well. In a tariff world, the need for redistribution is less - factory workers get the money directly in the form of a paycheck etc through their protected jobs. In a non-tariff world, these jobs no longer exist but the government would ideally now offset that loss through investments in education, infrastructure, new job opportunities etc.

Hope this answers why globalism is supposed to work and where it may not be working.