Your cumulative bill for the Iraq war: $1,020
Your share of the bill is impossible to calculate on a general basis, but let's try with some 2006 Census Bureau numbers. If you calculate by the number of individual Americans over 25 (195 million), you get a bill of $4,360. Only 152 million are in the workforce, so that makes the bill $5,592. If we go by households (112 million) it's $7,590.
Where it gets really complicated is that if you make more money, you pay more taxes -- and a higher percent of the taxes you pay go to the federal government, not social security. The Congressional Budget Office divided the population into fifths by their income. The highest fifth (or quintile) made an average $231,000 pre-tax in 2005. They paid 86% of federal income taxes. (This calculation leaves out not only Social Security, but also corporate and excise taxes.) That means the top 20% (or 28 million households) paid 86% of the $850 billion or $731 billion. So the average Iraq and Afghanistan wars bill for those in the top 20% is now $26,100. The top 1%, who make an average $1.6 million pre-tax, pay 39% of income taxes, so their cumulative bill would be $30,136.
The American family in the total middle, who average $58,500 in 2005, pays only 4.4% of income taxes. If you divide $37 billion among its 28 million quintile, you get a $1,335. I think that's probably closest to the actual tab for the typical American family. That's $314 for Afghanistan and $1,020 for Iraq.
None of this, of course, gets into the real cost of the wars, our American dead and injured, and their families. Or even the broader economic implications. My friend Anna Bernasek did a much more thoughtful and insightful economic analysis in the New York Times of what the Iraq war cost the Iraq ($24 billion a year or 40% of GDP) or would cost America (roughly $1 trillion over a decade or 1% of our income.) And I'm not going to start on the interest on all this. Since we've borrowed the money for the wars, the actual tab is going to be higher, just like if you buy an appliance on a credit card. But if you're a typical American family, you've paid roughly $1,000 for Iraq.