> Even if it's implemented, how do you rise tariffs on intangible works?

If you are an American company (or a subsidiary thereof), and you have an employee resident in another country who does IT work, then you pay a tax to the US Treasury on that employee's salary. This tax can be varied depending on the country of the employee's residence.

Alternatively, if you pay OutsourceCo or whomever to provide you with IT services, then, depending on OutsourceCo's incorporated location, either you pay a tax on the services you buy from OutsourceCo, or OutsourceCo pays the tax on salaries just described.

All this can be avoided by hiring American workers, of whom there are many currently looking for work (mainly because of offshoring and immigration).