I work for a large medical company that has a call center in the US headquarters and have also been outsourcing their call center to India and Phillipines. From what I can tell from my observations, by the way I am not directly involved in the call center so my comments are not quantifiable, people anywhere eventually tire of working for shit jobs.
Perhaps people outside the US can last longer than their American counterparts, but over the course of time they eventually develop the same traits that cause them to be terminated as well. Bad attitude, lack of interest, insubordination, lack of job performance. A crap job is just that, if you are hungry then you may accept it, but once your basic needs are met you will realize you no longer wish to be in a crap job. Americans have their basic needs met more easily, than the countries mentioned so they tolerate a bad job in a less amount of time than people that have not eaten or had a decent place to live for many years of their life.
Complacency is human trait not just Americans.