Whether it was our fault or not, like any other disaster the United States is in a unique position in the world to lessen the global impact. We are richer than other countries and it would be stupid to allow global consequences that ultimately affect the U.S. too without trying to help.
The United States, and all countries and all people, should always be trying to lessen environmental impacts. We were put on this planet together with many other forms of life, there's no reason we should not try to conserve other life. The human race is great, and very evolved, but we need to give back to this beautiful world we live in.
The US should do everything that it can to help lessen the environmental impact of Chernobyl. Besides being the right thing to do, it has environmental effects that spread the entire globe (of which we are, undeniably, a part). I think that the US has a responsibility as a world leader to lead the mitigation of environmental issues, whether we were involved or not.
The United States should contribute more to help lessen the environmental impact of Chernobyl. Chernobyl was a devastating radioactive disaster, and due to the properties of significant amounts of radiation, those negative effects are still prevalent today. The United States has a duty as a world power to help out in global matters, including Chernobyl.
There's not much to be done for Chernobyl anymore. The sarcophagus was built around the reactor to contain the worst of the radioactivity, and the radioactive cloud settled back out of the atmosphere long ago. The only thing left to do is wait for the radioactivity of the region to finally exhaust itself, and there's no man made process to speed that up.