Yes, you DO have to pay US income taxes.
It is in your best interest to pay the taxes and to file a return. Once the return is filed, the IRS is limited in how long it has to audit yuou. An unfiled year is always open to audit.
There are some who wrongly think that the US income tax is unconstitutional as the States did not pass it correctly (wrong signatures, etc). Whether or not this is true, US courts have consistently ruled that the tax is constitutional. People who do not pay taxes or do not file returns can be put in jail AND owe the tax anyway. The IRS can put a lien on your house, car, bank accounts, garnish your wages, etc. The IRS is the worst creditor you could ever have. They do not have to abide by the same terms as VISA/MC and other creditors. Plus, when you owe many back years...you probably have lost the original documents needed for deductions. Without the proper documentation, the IRS will deny you the deduction. In short, it is better to pay your income taxes. Plus, if you need to get a passport or other gov't services (social security)....you may be out of luck.
You can get an accountant to help you file those past 3 years. You will have a clean mind and be able to sleep at night.
If you don't like the war, then punish the President and Congressmen and Senators. The IRS is just the collection box for the people VOTED into office. By not paying your taxes, you hurt the troops & the rest of us who pay our fair share.
Skeeter