Nope, we are rising in power, not declining.
Have you paid attention to American demographics lately? Nevermind global empire, do you really think that a USA where whites are a minority, and where anti-white racism is accepted and commonplace, will be a place worth living in?
Besides, 15 years ago, the USA could have easily defeated China in a war. Today, the outcome is uncertain, to say the least. China is growing more powerful by the day. And, in a few years, their economy will be the largest in the world, relegating the USA to the #2 spot.
The USA is self-evidently in decline.