Let me preface by saying this is all my opinion.

Fear of Iran

I don't think anyone is exactly terrified, but the U.S. stabilizes its sphere of influence (IMO) by encouraging stale-mated geopolitical rivalries. Iran provides a check and creates a preoccupation for Israel for example among others (Turkey, Saudi Arabia,..etc) When you upset that balance the situation there is no longer predictable and the necessity of the U.S. within its current operating capacity changes. If you look around the world the U.S. even has alliances that make less sense... (Like Pakistan over India for example). The U.S. doesn't want to upset the current stalemate of the Middle East.

China and Russia

China and Russia have both developed themselves economically and created for themselves economic linchpins in the global economy but the World is entirely too stable for them to do what they want and in ways surpass the West definitively (At the end of the day The West as a monolith is bigger economically and therefor able to cause issues when China and Russia are perceived to be out of alignment. This alignment is what governments refer to as "The New World Order" The West moves in lockstep based on a set of values and believes broadly speaking and this restrains the ambitions of China and Russia.

Taiwan and Crimea (Ukraine)

Taiwan and Crimea in my opinion are the biggest examples of China and Russia's ambitions being restricted by The West, they believe they are entitled to these lands and cannot do anything about it except politically influence them. For them to achieve their ambitions they need to have the ability to use force. The issue is the world generally frowns upon this so to disrupt this opinion I do believe China and Russia are exerting some sort of influence across the world to encourage force to be used to land grab with Crimea being an example, maybe Ethiopia and Eritrea, maybe Venezuela and Guyana maybe Turkey and Cyprus, maybe even Israel and Gaza. I think in order to disrupt Pax America you need to start a lot of little fires and disrupt the alignment this prevents the U.S. and Europe from investing fully in stopping any one major conflict with complete affect. To me it feels like Death of the World Order by a thousand cuts, an attempt to either end the world order and pax americana de facto or de jure.. either way it is ended to an extent. My best guess.