The invasion of Afghanistan was a bipartisan decision, and in fact both parties, republicans AND democrats, both vied for the position of being seen as the driving force behind its inception (based on the notion of which party was the most 'patriotic'). Maybe you weren't old enough to see that unfold, like I did. Or maybe the partisan politics of our system have coaxed you into forgetting (very common). The only reason the invasion of Afghanistan went down in history as a republican initiative is because the republican party has traditionally been the party of pro national defense, so the democrats were fighting an uphill battle to look like they initiated the conflict. Dont believe me? Look it up.
The invasion of Iraq had support from many nations, and most experts agree things are better in Iraq now than they were before we invaded. Tell all those tens of thousands of muslim women who are now allowed to go to school, that the war to free them to make their own choices in life, was 'imaginary'.
As for republicans wanting to burn obama, you remember the bush era much differently than I do. If anything, democrats took their criticism to a new level of personal insults... how often were we told how stupid GW Bush was? Pics of him at his worst, sound bites of every mistake he made and every embarrassing situation he was in. As a relatively poor public speaker, a seeming inability to dance, and generally a bit clumsy, he was an easy target. And democrats took full advantage of every opportunity. So dont play this off as just some republican-only tactic of harassing the current commander in chief.