The russians built cheap, and they paid for it. The Japanese disregarded the very real potential of a tsunami, and they are paying for it.
The odds of either of those 2 scenarios in the USA are slim to none. Where it might be possible, you can bet that some changes are being made to mitigate the potential occurrence.
TMI was our meltdown, and nobody died or had to move away....and if the operators had left the controls alone and let the protection circuits do what they were doing, there would not have been a meltdown. The operators didn't believe their instruments and turned off the safety system designed to provide emergency cooling. You guys can rant all you want, it won't change anything. Long story short, we would be far better off teaching the next generations how to use less energy....the current generation is too addicted to want to change their habits.
NRC: Backgrounder on Chernobyl Nuclear Power Plant Accident
The NRC has some info on how many cancers actually occurred....