If the United States lasts in its current form for another 100 years, I will be surprised.

100 years ago, you could argue this country was fundamentally different than it is now — aside from rights (pretty much all of civil rights) and liabilities we now take for granted (the concept of federal income tax was just 10 years old, and not even fully implemented for another couple of decades), we were still two states shy of the 50 we have now.

The country will absolutely change in the next 100. No telling which way, though.