The pervasive mythology of American exceptionalism is essentially a religious doctrine positing that the US is essentially a perfect nation. Consequently, any issues arising within the system are perceived as external threats rather than inherent flaws. This mentality fuels the polarization between mainstream Republicans and Democrats, much like a religious schism. Both sides have a different interpretation of the doctrine and view each other as heretic traitors intent on destroying the nation.
American foreign policy is essentially just age of sail imperialism but with “democratic” subbing in for “Christian”.
“They’re not Christian so we can kill them and take their stuff” has become “They’re not democratic so we can kill them and take their stuff.”
Also works on the next level because even if someone outside the European ingroup becomes democratic or Christian, that democracy or Christianity just becomes a lever of control for extractive economics.
Or you just accuse the democracy of not actually being a democracy, e.g. China