Governments are not unaware of the environmental impacts, so that impression is accurate.
Secondly, one take on the Iraq war was that it happened not to obtain fossil fuel resources, but rather to obtain control over them, and prevent them being exploited in a way which threatened the interests of US and/or Saudi oil.
“Cheap” in quotes because anyone who thinks it is cheap is not accounting for some significant hidden costs.
The tragedy of the commons applies here. If you are not familiar with that, it’s worth looking up. I’ll assume you are.
Government can have a role in mitigating the tragedy of the commons by having the industry pay for the problems they create.
Or government can look the other way, which is a defacto subsidy.
We didn’t used to be a net exporter. Part of the reason fracking even got the traction it has now is that government was alarmed by how much money they were paying for the oil wars, and got desperate for any way to stop the bleeding.
There are only a hand full of temporary cases of local well water contamination with benzene.
Implementing a new tax for CO2 emissions is a much, much bigger political endeavour than simply letting a subsidy expire and not renewing it.
That's why there's not much value in perverting language to somehow argue that fossil fuels are subsidised. They are not, there's no way to "remove subsidies from their dirtier competitors", as the parent poster suggested.
There is a way to tax CO2 emissions, but that's a different discussion altogether.