Neighboring nations should feel threatened by China's increasing interest in disputed waters and natural resources because it has repeatedly demonstrated that it does not care what other countries think of its willingness to do things that are contrary to world opinion. They are not afraid of anyone and this is becoming dangerous.
Yes, China's neighbors should fear its increasing interest in disputed waters and natural history. We need only look at history to see what happens when one country wants what another has. Both Japan and Germany attacked neighboring countries for their natural resources, starting World War II. War and other forms of aggression seem to be the only outcome of China's regional disputes.
China historically has made both land and water grabs from their neighbors. They have done so by force, and they have done so by threatening other countries with economic harm if they do not comply. Given the lack of information that comes out of China, and the propaganda, other countries should certainly be worried.
This is why China is going to surpass us. They believe in science and emphasize education. We believe in superstition and don't want to spend a nickel for natural resources. When U.S. were big on research back in the 60`s, U.S. were the leaders. Now we have a group that can't even understand the science behind climate change. And if you believe that science is lying to you, shouldn't be much longer.