It's not simply accepting defeat that poses difficulty; it's being anything but the best, and first, and most able. American exceptionalism isn't just a cliche, it's a cult of identity, a nationalist truth that cannot be abridged without violent opposition.
Well, exceptionalism is a cult that is part of American education and media since early childhood. It is not just nationalism (loving your country), it is ultra-nationalism that preaches the idea that they're superior to other countries.