Being the dominant species on Earth, humans make their own rules and requirements on how things should be. It is not how things should have been according to the law of nature. Because of the danger that these snakes pose to human lives at Guam, the U.S. military decided to kill the snakes. Because humans want to protect their own interest i. e. the tourism industry of Guam, they decide to kill the snakes. Because of the fear of these snakes encroaching into Hawaii, the snakes are to be killed. We can see that the humans are selfish and care only their survival at the expense of killing the snakes!
As killing is heavy negative karma, Buddhists will not advocate killing the snakes. However, humans lives are at stake too if the snakes are not killed. Hence, killing are involved in either case. Pujas are usually recommended to be performed to appease the snakes and to dedicate merits to them before the snakes are terminated.