There is nothing that the United States could have - or should have - done regarding those protests in Iran. Any interference/support for the protestors would have caused more blood to spill, and produced the same outcome.
The United States should be urging China to resolve this peacefully rather than remaining silent. That's not hard. And it is not dangerous. And it is not neoconservative.
Instead the president has promised to remain silent.
Leader of the free world!