According to reports from both US and China, Trump and Xi  had a very good meeting at Mara Lago with both sides happy with the results and improved relationship. China is key to controlling North Korea. Only China can impose really severe sanctions on North Korea because it has important trading and aid relationships with North Korea that no other country has-- China has a lot they can take away and we have nothing to take away as far as sanctions. Militarily, only the Chinese can respond quickly with massive military strength against North Korea because of their shared border. Bringing in the carrier group improves US ability to attack or defend. There are no really good military options, though, because of North Korea's ability to retaliate quickly against South Korea and Japan, including the use of nuclear weapons. Having a carrier group nearby will make North Korea think twice about any military action of its own. Ultimately, China has the upper hand here to help us.