Какие-то нац парки могут быть полностью закрыты, какие-то будут работать, но с ограниченными сервисами. Сайты парков поддерживаться не будут и могут содержать недостоверную информацию. Cмотретьт надо конкретно по каждому парку. Joshua Trees и Grand Canyon, например, будут открыты, White Sands закрывают.
С сайта Grand Canyon
Government Shutdown
During the federal government shutdown, this website will not be updated and may not reflect current conditions. Some national parks may remain accessible to visitors; however, access may change without notice. Some parks are closed completely. Some visitor services may be available when provided by concessioners or other entities. For most parks, there will be no National Park Service-provided visitor services, such as restrooms, trash collection, facilities, or road maintenance. For more information, see http://www.doi.gov/shutdown and the park website.