People in the States / People with US Citizenships
The US Senate Committee on Foreign Relations has 18 members that can all be reached directly through email or phone.
Below is a list of these members and their contact information.
The least you can do is send an email or make a call to voice your opinion on the war.
Phone: (202) 224-4814
Email - firstname.lastname@example.org
Phone: (302) 573-6345
Email - http://biden.senate.gov/contact/emailjoe.cfm
The remaining 16 members' contact information can be found here.