Manages national wildlife refuges that serve as wildlife havens; encourages hunting, fishing, wildlife observation, photography, and environmental education.

Wildlife national parks serve as refuge for the natural wildlife and protection from outside world.

Explanation:

As these parks are made for conservation reasoning, often large parts of land  either natural or artificial like the yellowstone national park in Wyoming and Yosemite national park in U.S these tend to provide a heaven for environmental education and photography these are good places for visitors and have set an example for environmentalism in the country.

the only other powers were germany russia and uk and they were too busy fighting each other wearing each other down   that the us was becoming strong and they were becoming weaker