Not sure if English is your first language so I will go lightly here. For the most part Presidents cannot declare war without approval from Congress (there are exceptions that have been well documented on this site, see the Syria threads). Bush did have to go to congress for approval to attack Iraq. There are many reasons why Bush won a second term, despite the fact that WMD's were not found, many felt that he and his administration were simply wrong not lying. Lastly, President Obama has not continued to insist on missile strikes against Syria now that they are complying and giving up their chemical weapons.
I agree with Loki on this one. Obama is no longer insisting on missile strikes and George W. Bush went to war with Iraq based on imperfect information from the Defense Department and CIA.