Firstly, you got your facts wrong. Most Shiite members of parliament attended, some Sunni attended and some boycotted and most Kurd members boycotted. Nevetheless, those who attended the emergency session of Parliament, voted in favour of kicking out the US.
Furthermore, Iraq had once kicked out the US (Bush administration), under the Nouri Al-Maliki government.
Afterall, its their country.
Are you saying another military (say Australia) go to visit the US, and when the US government asks our military to leave - we should say stuff you?!?