This is exactly how the IRS treats all non-resident US tax payers. My ex, a joint Canadian/US citizen, had a problem with her taxes one year. The CRA (Canadian Revenue Agency) sent a letter that basically said "You appear to have made a mistake on your taxes, we think you owe an extra $XXXX. Check with your accountant, sorry for the bother if this isn't correct." the letter from the IRS basically said "You have defrauded the US Government of $YYYY. You will be arrested if you return to the US. You will be extradited if your country of residence supports extradition for Fraud. Fraud of this amount can result in <list of horrible penalties>"

Her accountant cleared it up in a few days, apparently someone at the IRS had made a mistake about Canadian Tax Law and reported the problem to the CRA which didn't verify it. It was a scary couple of weeks until we got the letter from the IRS which said the taxes were fine but included a warning about not letting this happen again.

I'd have renounced just for that bullshit.