It's an APEC summit, not a Bushfest. They're cracking down on security because we have the heads of state of the entire Pacific Rim here.
To read this stuff, you'd think security was never tightened in Sydney before, nor everyday citizens inconvenienced. It happens quite often. Royal visits and the annual Gay and Lesbian Mardis Gras are two examples.
As for "would this happen were Howard to visit Washington?"; if he were attending an APEC summit hosted by D.C., you bet!!
Calm down people, before you burst a blood vessel! Take a deep breath, sit back in your favourite chair, and relax.