No, getting cheaply made crap even cheaper is bad for the American people because it drives out competing cheap but high-quality US- and Canadian-made products.
And that is the primary reason that China subsidizes shipping costs for Chinese manufacturers: to drive foreign competitors out of business until only China is left.
The current scheme allows me to cut out expensive middlemen for quite a bit of products. Middlement that don't add anything I value to the equation.
Alternative is getting the same or maybe at best rebranded chinese OEM products, that went through a local distributor that adds his own markup, taxes, and other stuff, because he's operating in bulk quantities.
Changing the current scheme will be bad for plenty of consumers around the world.
It will also make it more expensive to get replacenemnt parts, for typical electronics, and will make self-made repairs more expensive. Because normal (unatuhorized) people can only get many of those spare parts from China.
Making it more expensive to ship from China will have many negative effects. It may have some positive ones, but that's to be seen.
Assuming you are an average mail user, you can still buy directly from China, no middleman, and spend the same amount of money you always did. The difference is that the cost will no longer be hidden behind abstract government subsidies.
If a middleman ends up cheaper because of bulk shipping, that's because they're actually providing value! They are reducing the total cost of shipping.
If the total shipping cost you pay, including your share of hidden subsidies, goes up? That means you were an above-average china-buyer, and the average citizen was paying part of your bill and getting nothing. That's not fair, and you're not entitled to offload shipping costs onto everyone else.
You assume taxes will go down as a result of this, which is most certainly not the case. They'll just be redirected to something else, perhaps something I don't care as much about.
And I'm also paying quite a bit of taxes that go to someone else's needs, and I have nothing from. Just a nature of taxation and government subsidies.
This just shifts the balance of what's comming back to me, to where I don't care as much, perhaps.
And that is the primary reason that China subsidizes shipping costs for Chinese manufacturers: to drive foreign competitors out of business until only China is left.