Individualism is at the heart of the American identity, it has little to no sense of a collective purpose. The idea that your destiny is yours and yours alone and is not intertwined with the destiny of others.
That helps us achieve amazing things, like people making trillion dollar companies out of a garage. It also inspires things like mass shooters, who hate collectivism more than anyone, which is why they usually shoot up groups of people indiscriminately. It both enabled and cripples America