On 11 March 2011, northern Japan was rocked by first a magnitude 9.0 earthquake off the eastern coast and then an ensuing tsunami. The Fukushima Daiichi Nuclear Power Plant complex was hit by these twin disasters, and a cascade of events was initiated that led to radionuclide releases causing widespread radioactive contamination of residential areas, agricultural land, and coastal waters. Radioactive material from Japan was subsequently transmitted to locations around the globe, including the U.S. The levels of radioactive material that arrived in the U.S. were never large enough to be a concern for health effects, but the presence of this material in the environment was enough to create a public health emergency in the U.S. The radiation safety and public health communities in the U.S. are identifying challenges they faced in responding to this incident. This paper discusses three of those challenges: (1) The growing shortage of trained radiation subject matter experts in the field of environmental transport and dosimetry of radionuclides; (2) the need to begin expressing all radiation-related quantities in terms of the International System of Units; and (3) the need to define when a radiation dose is or is not one of "public health concern." This list represents only a small subset of the list of challenges being identified by public health agencies that responded to the Fukushima incident. However, these three challenges are fundamental to any radiological emergency response. Addressing them will have a significant positive impact on how the U.S. responds to the next radiological emergency.