The gap isn't that huge. There is a little difference on their opinions on guns and war, but not as much as you would think from hearing how upset people get about it. Both sides in Washington are trying to keep drug laws the same. Both parties are willing to go to war--they are usually arguing about what is worth going to war over, whether the US should do it alone or seek international support, and how it will be paid for. With guns there are a lot of people who are of the opinion that "the liberals" want to end private gun ownership and a lot of people fear that almost any method of registering or licensing guns is a stepping stone to that end, but that view seems to be limited to a few democrats. A lot of democrats own guns and support gun rights, but Obama and a few others were quite loud about asking for more than simple background check legislation, and basically stopped themselves from passing anything the same way the Republicans stopped themselves from passing any immigration bills. On energy, they aren't too far apart either. Both support shale fracking and issuing more permits for oil production--the debate usually centers around controversial areas like ANWAR and offshore drilling.
Basically, other than a few anti-gun ownership types on the left and a few 'why do we even have nature preserves' types on the right, people agree on the basics. They just get hung up on a detail here or there to score some political points for the cameras. If a democrat suggests it, a republican will say it is stupid and vice versa--even when they actually agree. If a democrat suggests it and a republican fixes it, then they both get to claim credit--and that is what half the argument is about.