It's a little bit late, but it can be helpful for another person.

You can hide this field with an inherit on the XML view like that :

<record id="view_partner_form_inherit" model="ir.ui.view">
    <field name="name">res.partner.form.inherit</field>
    <field name="model">res.partner</field>
    <field name="inherit_id" ref="base.view_partner_form"/>
    <field eval="1" name="priority"/>
    <field name="arch" type="xml">
        <xpath expr="//field[@name='state_id']" position="attributes">
            <attribute name="invisible">True</attribute>
        </xpath>
    </field>
</record>

It's working on the V7.

The address format can be changed in the Country settings. Just change the format here.

Thanks this solutions was the best because hide the field but dotn generate problem, but when you put replace the field the openerp genere the problem

Update your code, it works well at newer versions (Runbot).