You can't fix something that is way beyond repair.
For any nation state to exist, there are certain criteria that needs to be present. For most successful nations that stood the test of time, we can see that having a predominant homogenous racial and ethnic population, culture, and religion are some of the most important factors. However, once those items are no longer present, that nation state will become unstable internally. Moreover, once you factor political and economic corruption, runaway national debt and money printing, unsustainable imperial foreign policy, etc., that nation state will eventually collapse.
The US republic is long since dead; and the oligopolistic-lead US empire is on its last decade(s). Can America turn things around? Probably not, as history has already showed that once your nation is in decline, you are already, on your way out, like the other failed nations, in the past.
Even if Trump manages to stay in-power, for the next four years, what happens after? Will democrats and republicans come together and unify as one?
America is internally divided more than ever and that appears unlikely to change, in the future. Hence, the end of America, in its current nation state form, is inevitable.