> allowing the Chinese to steal our technology and then underprice our businesses with cheap labor [is not beneficial to most Americans]
This tariff isn't preventing that, or punishing the Chinese companies involved.
> The reason they're the only viable place to purchase these items is because they're so cheap. Making them more expensive gives space for non-Chinese competitors to enter into business.
This tariff makes American assembly of Chinese components more expensive than it already is. Finished goods made in China are unaffected.
For example, an assembled-in-china iPhone will stay the same, but the moment this comes into effect, the cost of making the Mac Pro in the US will go up substantially.
To avoid this, apple can either:
1. Shift Mac Pro assembly to any other country.
2. Switch out all their suppliers and components to ensure that nothing comes from China.
Most products have done #1 without the tariff. The tariff just makes it harder to justify keeping anything in the US.