This might be kind of lengthy but here are some of mine:

Democracy will come to an end. One thing that's true across all history is that democracy is temporary. It's slow, it's clunky, it's complicated and bureaucratic, and in desperate times democratic societies will gladly return to dictatorial rule to restore order because that is the natural state of government, democracy is unnatural. America is no exception to this. Democracy can only exist when a society is at peace with itself and that's only if the people even want it.

Pax Americana will come to an end. Pax Americana refers to this era of relative peace brought about by the United States since the end of WWII. I could see isolationism (or at least non-interventionism) becoming mainstream again. More and more Americans are getting fed up with our government spending recklessly on foreign wars all while the cost of living continues to rise, also, younger Americans no longer feel the kinship with Europe that previous generations did and feel less of an obligation to protect them. I could see the US closing all it's European military bases at some point later this century due to unpopularity.

America and Europe will no longer be allies. Much like in my previous comment, Americans and Europeans will just lose their kinship with one another. Nothing bad really happens between us but we'll just culturally drift apart as our civilizations ideals diverge. It'll reach a point where we'll see each other as completely separate and distinct civilizations instead of being united as "westerners." For any history buffs out there it will be similar to the divergence of Roman and Greek civilization leading up to the Great Schism.

Racial demographic changes. This one doesn't need much explanation, white people aren't having as many babies as other racial groups and will steadily decline in terms of percentage of the population. This will have profound impacts on American culture, however it will remain overwhelmingly Christian. Which leads me to my next point.

Another great religious awakening. As America's racial demographics diversify we could see a push to put Christianity back in the center of American culture as a means to unify. Religion is the best unifier as much as its the best divider, but in order for this to happen, the southern white evangelical flavor of the religion needs to die as it's extremely unpopular.

These are just a few because I didn't want the post to be ridiculously long, and I tried to keep them fairly grounded in reality and nothing crazy. But let me know what you think and what predictions you may have?