No one picks fights with big athletic men unless they are bigger more athletic men or the potential victim is known to be unwilling or afraid to fight. Then all bets are off.
American has the capability to trounce any other country on earth yet under President Obama we can't get any hostile foreign country to do what we want. Obama couldn't reach an agreement with Iraq on legal protection for our troops so that now, without a minimal US presence to provide support to the Iraqi military and police terrorism in Iraq, essentially eliminated under President Bush, is once again a booming business. Due to Obama's incompetence Iraq may end up worse than it was, in terms of being a threat to the US, when we liberated it thereby essentially wasting the lives of all the Americans who died there.
Is it surprising after things like that and Obama's infamous bowing apology tour where he lauded Islam and said how bad the US is that Syria paid no heed to Obama's red lines? In a world where terrorists can kill a US ambassador and the Secretary of State says "what difference does it make now" what self respecting mass murdering dictator is going to lose sleep over a threat uttered by the school yard coward?
Any country that fails to show resolve is doomed to have to fight; just ask the British about Czechoslovakia.