The largest tsunami ever recorded (the 1958 Lituya megatsunami in Alaska) reached about a half a kilometer inland. While this is a really far distance inland for a tsunami, it is still considerably smaller than most coastal countries.

For example, the smallest island country in the world, Nauru, which is in the ocean off of Australia, has an area of 21 km². So even this megatsunami that reached half a kilometer inland would not have reached the middle of this country. Thus, it is unlikely that a tsunami would be able to hit the middle of a country.

There are many factors that control how far a tsunami will travel across land once it reaches the shoreline. In general, the furthest a tsunami will travel is up to about 10 to 20 miles inland. This number is very dependent on the topography of the land the tsunami is traveling across as well as the amount of energy the tsunami contains.

Usually, tsunami’s don’t travel more than about a mile or so inland. So, some factors that control whether a tsunami will travel far across the land is based on how high a tsunami is, the source of the tsunami (tsunami’s that result from long ruptures on the seafloor, like from an earthquake, will produce long waves that lose much energy as they travel through the ocean), the shape of the seafloor, and the shape of the land the tsunami is traveling across. If a tsunami is hitting land with large mountains close to shore, then it is likely the tsunami will not travel far. But, if much of the land inland is very low-lying and close to sea-level, then the tsunami may travel much further inland.

If the country is a small island nation like Fiji and the tsunami is something enormous like what an asteroid impact could cause, then yes. Tsunamis behave in a lot of ways like temporary increases in sea level, so a huge tsunami might be able to wash over a place like Florida but there's no way it would get into, say, Colorado.

Tsunamis are ultra-big waves. They aren't as big when they're in the open ocean, but they get taller as they come into shallow water. But there is a limit to how far they can travel inland. This depends on the height of the wave, and the speed that it is going. So anybody who's living in the middle of America definitely doesn't have to worry about being drowned by a tsunami!