well, USD is only suffering from one, severe decline:
There is an epic historic struggle occurring in the world even as we speak. The BRICs nations are attempting to "de-americanize" the global economy.
In response, TPP and TTIP are part of an agenda put into place by some 600 of the largest corporations in order to impose US dollar hegemony on the rest of the world.
The purpose of taxation is to force the population to use government issued currency, but since the US cannot impose taxation on the citizens of other countries we have the petrodollar. Fuel cannot be purchased without US dollars in the current system so what is happening is essentially a matter of the US attempting to bring the entire planet under its direct political and economic control.
Don't think Russia and China are pushovers. They have already forced the US and France to break off a sneak attack on Syria in 2013. This event was equivalent to to the Cuban missile crisis but wasn't mentioned at all in the US media. This is the real reason behind the Ukraine debacle and the current anti-russian propaganda efforts.
Expect major conflict. This hand has been dealt and all that remains is to play it out.