Of course US security and foreign policy doesn't change from president to president. The president is allowed to tweak a few things around the edges, but the core policies have been developed by the Depts of State and Defense over decades, and they are not about to let some guy who is only around for a maximum of 8 years dictate how things should be done.
Haven't you ever seen 'Yes, Minister', and its sequel, 'Yes, Prime Minister'? The government is not about to let a bunch of mere politicians tell them how to run the country. I have no doubt that this is just as true in the USA today as it was In the UK a few decades ago. By the time a president has had time to even begin to influence policy in a really large government department, he is out of office, and his successor is trying to undo the things he hasn't yet had time to get done.
A good president can be a powerful positive influence; but government has a lot of inertia, and any positive (or negative) policy changes during a presidential term in office is as likely to be despite the president's best efforts as they are to be caused by them.
It takes a string of good presidents to influence policy for the better; and it takes a string of bad presidents to influence policy for the worse. Sadly, runs of good presidents are rare, while runs of mediocre and positively bad presidents are common; and really bad presidents have a disproportionate influence, because they tend to be unaware of the harm that can accrue as a result of actually doing things. Good governments, as Sir Humphrey Appleby would no doubt agree, are governments that resist calls for change.
In the broader sweep of things this is certainly true. A candidate like Ron Paul, advocating that we get out of NATO, simply isn't going to get elected. It doesn't matter that the proposal might be perfectly reasonable since NATO's purpose has been fulfilled.
But Clinton, Bush, and Obama have continued policies that they actually promised to end. Obama promised to get out of Iraq within 16 months. In fact, we stayed for the entire timetable that the Bush administration had negotiated. Bush said he would not engage in nation-building. (And remember that Gore had specifically endorsed nation-building during the campaign).
In fact, the public put the Democrats in power in 2006 to get us out of Iraq. Then they elected Obama to get us out, and when he didn't they gave Republicans control of Congress. And the public only re-elected Obama in 2012 because the Republicans nominated a Mormon and the evangelicals stayed home.
The public has wanted us out of Iraq and Afghanistan for a long time.
So yes, continuity in long-term policy is to be expected and is probably wise the majority of the time. But long term is NATO. It's alliances with Japan, Taiwan, and South Korea. It's the Rio Pact. Long term shifts are rare and the public usually ready for them when they occur (As, for example, Nixon's trip to China).
But we're talking about short-term policies here for the most part. It took about three years of the public to tire of the Vietnam War. Iraq was even less supported. We never thought we'd be in Afghanistan for 14 years when that war started.
Our relationship with Russia has been terrible, and that seems to have started under Clinton so it would take a Nixon-like figure to turn that around. That's a long term thing and there's no public pressure to change it (although I wish there were). Likewise with Iran. It takes a long time to overcome old animosities and public stereotypes.
But that isn't the policies I'm talking about here. I'm talking about policies that have generally been rejected by the successors until they get into office. The failure of sanctions against Saddam begged for a change in policy there, but toward a normalization with Iraq not an escalation.
The Israel-Palestine dispute begs for our benign neglect. Nobody has been able to make any headway there despite all of our efforts to force a negotiation. We should quit trying. Both sides have motivation to end it, but we can't force the issue.
In fact, nearly all of our interventions since the Cold War ended have turned to shit if they didn't turn out badly from the very beginning.
The second Lebanon War was a huge blunder. Libya has produced nothing beneficial for us. Iraq is descending into civil war. We turned an island of stability (if a rather authoritarian one) into a long-term trouble spot. Syria will also take a long time to return to stability after out intervention. These are short-term policies, but each president keeps repeating them only in a different place.
