Boomer prosperity and juggernaut (un)stoppbability read as orthogonal functions on my chart.
It's fair to say that in major conflicts since 1992, and perhaps going back earlier (1980s, Grenada invasion), the US was generally more successful, though even that's somewhat conditioned. During the 1990s especially, it picked its fights and especially in Gulf War I didn't fight to occupation.
At the same time, it did see several notable failures. GWI was prompted by a failure to respond in an appropriate or timely nature to Iraq's beligerance toward Kuwait, despite a very obvious intent. There was the Blackhawk Down incident in Mogadishu, Somalia (1993), a largely successful though not unmarred campaign in the Bosnian-Kosovo civil war, the failure to intervene in Rawanda.
And then there was 9/11. The single deadliest attack by a foreign power on US soil in history, and against which the entirety of the US defence and intelligence establishment proved utterly ineffective. (A gay rugby player and a few civillians provided a more effective protective force.)
Since 9/11 the US has been engaged in a legitimate though ultimately futile conflict in Afghanistan, as well as the utterly illegitimate and disasterous Iraq campaign, as its principle boots-on-the-ground conflicts.
There've been numerous other engagements (Nepal, horn of Africa, Syria, Maghreb, Pakistan, Indian Ocean / Somali pirates, Somalia, Libya, Uganda, Yemen, and subsequent actions in Iraq, but all have been limited engagements, most strongly reliant on airpower (manned and unmanned) or advisory roles, geared more at suppression than conquest and control.
The conflicts in which the US walked in and kicked ass are largely limited to the Spanish-American War (1898), WWI (as a late and limited participant), and WWII (as a major and decisive participant). Unless you'd like to count numerous labour disputes in which US armed forces attacked labour on behalf of industrial and investment interests.
On nuclear / WMD adversaries, "MAD" is in fact the principle doctrine of the atomic-weapons era: mutual assurred destruction.
https://en.wikipedia.org/wiki/Mutual_assured_destruction
I'm not making any arguments of ascendency or decline. I'm stating the historical military record.
(I did in fact study some of this in school, for what it's worth.)