Now:
Italian taxation on interests and dividends is lower. I would owe roughly 3000 dollars per year to the IRS (2004-2008).
Owe $3000 a year to the IRS? If you've already paid Italian tax at, let's say, 20% and you have a US tax rate of 30%, that $3000 tax at the difference of 10% represents $30,000 of income each year. So not just a few hundred dollars, but a significant amount of income you've omitted from your tax returns?
By the way, don't forget State taxes, unless you live in a state without an income tax.