Haven't we fucked up enough by invading and occupying Iraq?

Why are we now picking a fight with Iran?

5 Iranians Detained at Consular Office

American forces backed by helicopters raided the Iranian consulate in the mainly Kurdish city of Erbil in northern Iraq before dawn today, detaining at least five Iranian employees in the building and seizing some property, according to Iraqi and Iranian officials and witnesses.

And in the same article, a little recent history:

[...] in December the American forces detained two Iranian men in Baghdad and accused them of running guns and planning sectarian attacks. The men were later released.

Say, what is that I keep hearing about the sovereignty of Iraq?