The United States has an interesting system called streamlined procedures. As long as the amounts in question are low, there is good faith on the part of the taxpayer and the situation is not repeated, non-U.S. residents may not be fined and Americans would be fined 5% of the amount due. The fine is very low because this is a case that is outside a criminal or almost criminal context. It's an honest mistake. For someone—an immigrant, for instance—who does not understand the law very well and does not know how to apply it correctly, the fines are low. However, in all the cases where significant amounts come from offshore accounts and where there is camouflage, those are not covered by these streamlined procedures, and the fines are high.
On June 7th, 2016. See this statement in context.