The government does not do a good job with many things it takes our money to do, but the national park system seems to be working very well. From going to Valley Forge Park near where I live to Yosemite out west, I have been pleasantly surprised at how things are being cared for and managed.
Yes, in my experience, the American government does a great job in the managing of national parks. I have visited the Great Smokey Mountains National Park many times and have been impressed with how clean and visitor friendly it is. If it is any indication of the treatment of other parks, then the government is doing a great job.