This country has been built on the backs of slaves... those who believe the US to be a free country are more than likely beneficiaries...
A first line of defense for many of these folks is to quickly compare the conditions of this country to those of which the US has exploited...
I don't benefit from anything in this country besides my own hard work. You're gonna use slaves as a point? Almost every super power to EVER exist had slaves...not just the U.S. Slavery has BEEN over in this country for quite some time now. Tell Bill Cosby about slaves, or Ice Cube, Chris Rock, Richard Pryor (RIP). Oh, wait, those are entertainers, and ANYBODY can do that, right? How about Clifton R. Wharton, Kenneth I. Chenault, Roger L. Plummer, Alfred T. Mays, Carl Ware, Brenda E. Edgerton, Richard D. Nanula, or George R. Lewis. That's only a few black folks who grew in the U.S. and made something of themselves. People of EVERY background can benefit here if they work hard.
About the "defense" you are speaking of. A LOT of people have been outside of this country, some say other countries are better, some say the U.S. is better. I'm one of the people familiar with other countries, and there are TONS of things you take for granted. One example is, you're allowed to SPIT here. If a bug flies into your mouth in say, Singapore, you're not allowed to spit. It's against the law.
What else has been illegal in Singapore? Homosexuals are not allowed to live in the country, Bungee jumping is illegal, you may not walk around your home nude, It is considered an offense to enter the country with cigarettes. Guess what, Singapore is probably the cleanest country in the world. BUT, a lot of shit is illegal. Chewing gum just became legal.
In CHINA, Although the 1982 constitution guarantees freedom of speech, the Chinese government often uses the subversion of state power clause to imprison those who are critical of the government. There is very heavy government involvement in the media, with most of the largest media organizations being run directly by the government. Chinese law forbids the advocation of independence or self-determination for territories Beijing considers under its jurisdiction, as well as public challenge to the CCP's monopoly in ruling China.
References to democracy, the Free Tibet movement, Taiwan as an independent state, certain religious organizations and anything remotely questioning the legitimacy of the Communist Party of China are banned from use in publications and blocked on the Internet. The PRC is known for its intolerance of organized dissent towards the government. Dissident groups are routinely arrested and imprisoned, often for long periods of time and without trial.
Shall I go on?