Don't pretend like the US government has a good justification for this. It's purely another attempt to destabilize the country even more.
The entire purpose of these sort of sanctions is to hurt the public enough that they start putting pressure on their government to make a change that the sanctioning government wants. In this case the US wants Venezuela's government to be replaced with one who would be more friendly to US oil companies taking all of their oil and paying a small portion of it's value to the politicians who allowed them in.
The main reason Venezuela has been solvent up til now is that they have a lot of oil, which the government sells and uses to pay for social programs. But since the price of oil went down they've been having some money trouble. Combine that with the fact that Maduro knows as much about monetary policy as Trump knows about tariffs and you've got a deflating economy that's only made worse by sanctions, which again, is their entire purpose. They are specifically trying to ensure that Venezuela's government collapses so that US companies can move in and rob the region of it's resources.
Don't get me wrong, the best thing Venezuelans could do is probably throw Maduro out on his ass, but replacing him with some US-friendly bootlicker is worse than no solution.