The way the US tax treaties work you get tax credits for your local taxes. So if you live in Scandinavia with high taxes, say 40% you have enough credits to offset all of your ~30% US taxes. But if you are in a low tax country, say 20% you would end up still paying ~10% taxes to the US.

edit: And yes, if the citizenship is a good or bad thing is of course highly dependent on your other citizenship, your plans to study/work/live in the US, the country you intend to live in instead of the US and a number of other factors.