I don't doubt there is revenue out there, I'm just saying if the real reason you are doing this is for revenue primarily, it just doesn't jive with the realities. It's a gigantic, massive pain in the ass for everyone, raises a paltry amount of money compared to federal revenue, and don't forget actually enforcing this will requires 1,000s of new customs agents which as government employees come with considerably more cost than just their salaries.
There is a bipartisan desire to stick it to China, and that is really where this push comes from at the end of the day. If it were all about money, there is quite literally a list of 1000s of other items that would raise more revenue and not require such headaches (and costs that bite into the very revenue trying to be raised) to implement.