I just added tariffs into Government Simulator
's simulation engine and released it as version 1.4 on Steam.
So basically, you can now be like Trump, if you like:
The effect tariffs will have depends on how the internals of the country you are running look like, and they have limitations:
There are no individual types of goods on which you can impose tariffs, it is just an average factor, since the simulation isn't fine grained enough for this. It doesn't have a simulation running imports/exports between all the countries. But that would be something which would be also maybe cool to be added some day in the future.