The U.S. has helped other countries such as Laos to remove bombs left behind from the Vietnam War. So compensating Greenland for the pollution caused by military bases seems appropriate as a humanitarian gesture. It is also in the best interest of all nations to help clean up any polluted waters since we all share the environment.
America, not only placed bases on their land, but we failed to maintain and/or deconstruct them to remove our footprint. It is hilarious that in our cities in America, in tiny suburbs, we have laws, rules, regulations regarding maintenance and lawn care of our own homes, yet, we cannot even keep the same respect for other countries. No wonder no one likes us.
More importanty, rather than simply throwing money at the problem, the United States needs to offer and provide help to clean up the mess that they have made. THe United States, and its people are often irresponsible this way and they will never learn and change if they do not feel the consequences of their actions.
Wherever there are riches, there are people who want to plunder them. Every single person on earth, including Americans, can think of a way that the United States has harmed them if only there is money in it for thinking so. The United States cannot go around apologizing for everything it has done. It would never end.