Bombing other countries isn't really libertarian, and that itself is one form of pollution that the USA does without environmentalists concern, not to mention humanitarians concern.

But you also might look at communist countries which have done massive destruction of the environment such as what the Soviet Union did to the Aral Sea: https://en.wikipedia.org/wiki/Aral_Sea

Another way states increase pollution is through fiat currency. When they expand their debt and expand the money supply they are destroying peoples wealth, which means they need to work and expend more resources to offset for inflation. For example, look at how much the price of college tuition and real estate have inflated. That means people are in debt much longer, and need to work more hours of their life, expend more resources to overcome these debts. And by increasing taxes to pay down the debt it also means that people have to work (driving cars and moving resources around) and expend resources for a longer portion of their life until they are unable to work anymore and are forced to retire.