All my thoughts on tariffs...

Protecting local industries:

While tariffs are an over all loss for the economy of a country, they can be effective at propping up a specific industries. The problem with that is then that you are encouraging domestic business to produce things that they don’t actually have a competitive advantage in producing. The classic example of this is sugar cane. Sugar cane is not produced in the States when left up to the free market. We just don’t have the optimal climate for it. We could enact tariffs which would cause US citizens to buy sugar cane from local producers. This would be at a much higher cost to those consumers, and we would suffer wasted resource from inefficient domestic production as we have encouraged American producers to spend their time on things that they aren’t actually good at. What is the opportunity cost there? What could those businesses have been producing instead that would make a lot more economic sense?

National security:

Now a common concern here is that things we need to produce certain things for safety and/or security. ‘we have to produce xyz in the country as a matter of national security.’ Two thoughts on this, one, I want countries to be interdependent, we are less likely to kill each other that way. And second, I think it would likely be far more efficient to just have a branch of the gov maintain factories that can produce xyz than it would be to distort the national economy to produce those things.

Taxes:

As it relates to taxes, yes tariffs bring revenue to the US gov, but that is still money coming from citizens. So it becomes a question of what is the more efficient way to tax US citizens, or which method of taxation distorts the economy the least? ...that gets complex, but this does not bring about a reduction in taxes paid by US citizens, it would just change how that revenue is collected and which parts of the economy are paying more.

I find the idea of switching from income tax to tariffs interesting, but, one, I have absolutely no faith that the gov would actually remove the income tax after enacting enough tariffs to cover the revenue(if we even could), and two, I think the distortion on the economy could be much worse than an income tax.

Other countries:

Any other country enacting tariffs faces the same situation. They are also experiencing an overall loss in their economy. Some places are doing it specifically to protect certain industries, and their reasons for doing that are varied. Maybe they want to grow that industry, maybe they also have some national security concerns, or maybe it's just plain corruption and the CEO of some big company's kid is married to the presidents kid and their industry gets special treatment. ...I think all of the above happens.

The motivation:

I can only guess at what Team Trump is thinking with these tariffs, but I find the idea that this is to encourage domestic production to be unlikely as these tariffs are not targeted and are very unrefined. If there is a grand plan to this I would imagine that it is either to force the reduction of interest rates(perhaps for debt refinancing), or to use as a bargaining chip with other countries.