1. War is NOT easy for any country - it can get really messy.
2. No, US will not attack any country out of the blue.
US was preoccupied with Iraq since 1991 and had no choice but to reshape its political landscape at a later stage (De-Ba'athification policy; 2003 - 2011). Of-course, American De-Ba'athification policy for Iraq wasn't an easy task by any measure and many people paid with their lives in the process.
FYI:
https://en.wikipedia.org/wiki/De-Ba'athification
3. Israel can take care of Hezbollah on its own. No, Turkey, Russia and Syria will not threaten Israel or even close; they have no stomach for opening this type of front because Israel is a nuclear power with SLBMs that can reach as far as Moscow in a short span.
4. I do not think that US is looking forward to execute 'regime change' in Iran at present; objective would be to damage/weaken Iranian regime to such an extent that it will collapse on its own weight. This is doable.
They threw his body into the ocean as to prevent potential terrorists/loyalists/followers to gravitate around his grave and use it as a basis to spread terrorism and/or recruit more people to their cause. Make sense on a second thought.