If the U.S. is not your home country you might be well advised to stay out of a poltical discussion, wherever you may be, until you are absolutely certain it is wise to do so. It's no secret that American politics have been a touchy subject for years, and the issues are best approached with caution. 

However, if you do plan to get into a discussion on American politics when travelling there, you should do some research before you go, and know at least some of the pros and cons of both sides. Often, it is hard to get a truly balanced and fair view of both sides of the issues by simply listening to international news, no matter how good the coverage in your country may be. Reading articles from The New York Times, The Miami Herald, The Wall Street Journal, and Fox News  are good places to start -- or just read articles on American politics from Google News (filter for those from American newspapers) for three to six months, and by researching statistics online (government sources are generally the most reliable.) All this should give you a good range of both conservative and liberal views on American issues. Don't assume you have a good grasp of the issues by simply watching your local or national news, or talking to friends, even American ones. Find out for yourself before you plan to discuss anything -- or at least plan to listen closely first and engage later. 

The United States is sensitive politically right now due to the deep divisiveness that has been wedged between the Republican and Democratic parties over the past decade, and a culture war that has been going on for even longer than that. There is a vast range in how people live from region to region – rural/conservative vs. liberal/urban, immigrant vs. nativist, rich vs. poor, religious vs. secular. Today in America, many news stories relating to these cultural divides are provoking everyday citizens into big fights, some of them violent,  so visitors would be well advised to figure out when and where their opinions would be welcome. They may unwittingly fall into a culture war they didn't see coming.

Some areas -- particularly Texas, the South, and Midwest -- are deeply religious. Some connect their religious beliefs to political ones, making issues such as abortion, the war in Iraq, capital punishment, or gay marriage impossible to debate. These issues are currently so contentious that nobody seems willing to change or even compromise their position, both on the streets and in political offices. When discussing these topics, bear in mind that some have lost their lives, loved ones, and livelihoods over these issues.

However, politically, this is a very important time for America: there are more immigrants within its borders than in nearly 100 years, many illegal. U.S. finances are in trouble, and many people are on the verge of losing their homes.  Americans have suffered the first foreign attack on the mainland in nearly two hundred years, and fears about unstable enemy countries with nuclear and biological weapons are a constant worry for citizens, the government, and allied nations.   (The United States, for example, is one of only a handful of repositories that stocks the cures for certain dangerous pathogens like smallpox.)

Americans are less than a year away from electing a new President into office (very likely from another political party), and already heated private debate is becoming much more public.  While some Americans believe that their government has been on the right track, ever growing numbers feel the opposite. The recent approval ratings of the incumbent President is one of the lowest on record and Congress's numbers are even lower. 

On the positive side, voter turnout in primaries and caucuses (pre-election races to pick candidates) is higher than it has been in many years, particularly with younger voters: 2008 saw a year in which televised candidates' debates had significantly higher ratings than the Oscars. (In most past elections where they coexisted the ratings split.) Many may look forward to discussing their country's politics with an outsider and might like to hear from a foreign perspective. However, personal attacks or ill-informed opinions will probably not be welcomed. On the other hand, simply agreeing with everything might also seem insincere. If you aren't ready to enter a political discussion, the best response might be to admit that you don't have a firm grasp on the issues yet.

Of course, like anywhere, use common sense above all. If you decide to go loudly and drunkenly "Bush-whacking" in any place sporting a mechanical bull and ten-gallon Stetsons, you might expect to find yourself in a pretty nasty confrontation in no time.