Why is it that USA space tech prefers water splashdowns instead of dry land like the Russians and Chinese?
"Softer landings" doesn't quite cut it as a reason, for at the speed of the impact, water is just as hard as terra firma. Then there's the risk of crew drowning and/or craft loss thru sinking. That doesn't occur in dry land.
Because landing in water means you can get away with a higher landing speed without putting too many Gs on the astronauts - ref the Wikipedia article on splashdown. The Russians (né Soviet) capsules lands on land because the Russians have so much open space available, but that means they have to carry either a larger parachute and/or one or more braking rockets to lower the impact speed to something tolerable. AFAIK the first Russian capsules that the cosmonauts rode all the way down - the jury-rigged Vostok they called Voskhod - carried their braking rockets attached to it's parachute lines...
A capsule landing on land also needs to be sturdier to take the increased shock loads, both from the impact and from the application of the braking rockets. This means you either needs a bigger rocket to get it up there, or less internal space for the astronauts / cosmonauts to move about in. A landing on land may not sink, but it does run the risk of taking a roll once it's down - ref Soyuz 18a.
Another reason given for the American preference for landing in water compared to the Russian preference for landing on land is the location of the launch sites. An American early abort will dump the capsule in the Atlantic ocean, whereas a Russian early abort will see the capsule come down on the steppe. That said, the current Russian capsules are rated for landing in water, just in cause - refer to Soyus 23 landing on a frozen lake and punching through the ice.
The Chinese seems to favour a land landing as well, which makes sense considering their landmass, lack of a large blue water fleet and the simple fact that their Shenzhou spacecraft seems to be based on / borrows heavily from the Russian Soyuz capsule.
In short; landing on water lets you get away with a lighter spacecraft, and does away with the need for a very large parachute and/or braking rockets. This means you can get away with a smaller rocket, or carry more supplies for a given size rocket.