Yes, the US will eventually follow Costa Rica's lead. I don't think the US will be able to be 100% sustainable in the near future. The country is simply too large. However, I think in the next 10 to 15 years, policymakers will realize that we do not have a future using non-renewable resources. Only then will the United States follow Costa Rica's lead.
The US increases its use of renewable energy each year but we are nowhere near where we need to be yet. We will do it in the next few decades though, as the people who have supported fossil fuels for long start to age out and drop out of politics.
No, I do not believe that the United States will follow Costa Rica in running on renewable energy. While admirable and important, I doubt the United States' ability to break free from fossil fuels and rely solely on renewable energy. Corporate interests rely heavily on the United States' relationship with fossil fuels and unfortunately, I believe that takes precedence over environmental concerns.
The United States definitely should follow Costa Rica's lead. We think of ourselves as the leaders of the world, so we should take the lead in clean, renewable energy. However, with the two main presidential candidates that we have now, I don't think much will happen on the environmental front over the next four years. Donald Trump doesn't believe in climate change and Hillary Clinton doesn't seem all that concerned about those issues either. Bernie Sanders would have definitely made those issues a priority, but he lost the primary. Therefore, I don't see the U.S. running on renewable energy any time soon.