Demographically, the US is more like several smaller countries amalgamated into one (the great melting pot). In the past, the glue that held it together was the willingness to compromise. The willingness to compromise came from the trust that everyone wanted what was best, even if they disagreed on how to get there. But today, everyone else is villainized; the opposing view is seen as racist, socialist, etc. If just one member of an opposing party votes for a bill in Congress, that is seen as a bad bill that did not go far enough.