You need to separate your thoughts here. There is no proof that the US staged the 9/11 attacks. Although, its your choice to believe in the conspiracy theories. Is there some questionable issues concerning the reasons for going to war, especially in Iraq, yes. i.e. David Kelly, Hutton inquiry, dodgy dossier. The terrorists acted out because of a long history of despising Western influence in the ME. They have committed atrocities against the West prior to the 9/11 and 7/7 bombings and the hostility had been building up for quite some time. The UK is the USA's closest ally, and for that, we are grateful. But just as in the US, your elected officials make decisions for your country. Whether you agree with them or not. If you disagree, then you vote them out.
We are joined at the hip, regardless on whether one or the other drags the other into poor choices. Pretty amazing historically given that we had a bit of a rough start two hundred + years ago. Oh, and there's that matter in 1812. ;)