Isolationism? Is it a "Good Thing"?

So, we are now in the middle of a nasty war in Iraq and Afghanistan.

Most Americans agree that we need to be in Afghanistan. That's where Osama (not OBAMA) planned the 9-11 attacks, recruited and trained the terrorists that struck.

Most Americans are doubtful that we should still be (or ever went into) Iraq.

So what about:
A. North Korea which is defying all international mandates to cease and desist in developing numclear weapons? A nuclearized North Korea will destabilize and raise the stakes in all of Asia and probably lead to a nuclear-weapon's armed Japan. (Yes, Japan has such advanced technology that the latest reports I saw indicate they could take that technology and make nuclera weapons within 6 months maximum).

What about:
B. Iran which is proceeding against all United Nations orders (resolutions) to stop their nuclear weapons development program whcih would destabilize the entire Middle East and probably push Saudi Arabia, Turkey, and some other countries to also "go nuke"!

What about:
C. Somalia and the south-eastern tip of Africa where war and al Qaeda terrorist camps are located? Somalia is the Afghanistan of Africa.

What about:
D. Venezuela where Hugo Chavez, the populist president is creating a new Cuba, eleminating all political opposition, nationalizing private companies, and planning a hostile, world-wide campaign against the United States? (Yes, Chavez may seem like a clown but he is a VERY RICH clown with vast petroleum reserves and a deep hatred of the US- he visited Saddam Husseing, Ghaddafy in Lybia, and even some of the knuckle-dragging dictators in the former Soviet Republics)

Should the US build up and use its intelligence, covert operations, and military might to try and reduce the threats from any of these (or other unlisted) dangerous places? If not then who will, the French?! If yes where does the US need to push back, how much, and do the Democrats and Republicans BOTH agree that we are the world leader and have some responsibility as a policeman of the world?

This is the puzzle that faces us all.