I deal with this quite often with my 2D art. I estimate over $200,000 in pirate sales in the last two years, most of it being very hard to track because it gets sold in shops, not on the internet. It's very distressing to me, because as a business, I lost money in these two years. So theft has actually put me out of business, and I won't be creating for the consumer market anymore.
What usually happens is that the supplier you deal with in China is either a middleman, or a factory that produces your samples to a terrible quality, so you go somewhere else, but they have your art. There are a lot of people in the pipeline that can get access to your work, and there is nothing you can do unless it sold from within a Western country.
Most of the product that gets sold on the internet is on spammy popup sites that add your art programmatically to various things, and automatically categorizes it in a product database that you can easily port to new site. Now since almost all of these sites originate in places like Indonesia, China, and India, there is little you can do to them but report the violation to paypal. It takes a lot of time even if you are using templates to send the DMCA claims. Paypal is actually very good about locking the accounts, but they are absolutely inundated, so a lot of times I have to send the same claim multiple times.
If the counterfeit product makes it to the US and someone is dumb enough to sell it, then you can go straight to the FBI, and since it is likely they are selling other counterfeit products, they will get swept up eventually. Usually though the accounts in the US are fronts for Chinese associates abroad, so you are dealing with professional criminals. They are hard to get at, but not all of them are smart.
The next recourse is suing the US based scammers, but there are not so many making it worth your while to sue. If the copyright it registered, then you can get a maximum judgement in small claims court, but it's nearly impossible to enforce. If these people had money, they wouldn't be stealing your design on a $15 phone case. If your copyright is not registered, you can register it, but you are only getting actual damages, unless you can angle for punitive damages on the counterfeiting angle. I haven't found a target worth doing this to yet unfortunately, but it's going to need to be open and shut for a lawyer to take it on contingency, and most corporations will settle with you quickly if they in fact screwed up honestly.
Anyway, that's my experience. It's very sad, and I lose my mind seeing all the progressive teenagers trolling about the excessive copyright protections, and justifying how pirating doesn't matter because they wouldn't have bought it anyway. That's simply not true. People are buying my designs daily, and since I don't get any of the money, I have stopped creating.
The real solution? I don't want to turn this into a political discussion, but as a feminist leaning woman, I am voting for Trump. I would vote twice for him as well if it wasn't a felony. The CBP is so understaffed, they don't even enforce tariffs on your average <$1000 package the vast majority of the time because the burden is too costly. How do you even expect them to enforce intellectual property rights without the bust be well north of seven figures? International trade is important, but the system really undermines the creative process of American companies seeking to innovate. Trump gets it right economically. If he does a tenth of what he says he will, it's going to be huuuuge for America.