The US doesn't have allies but a bunch of vassal states that it's milking. The alignment of these allies depend on the particular circumstances of the situation.
By your standard, do any of the considered "major alternative powers" (China or Russia) have allies?
Japan didn't break from US in this news article, it received permission to do so, likely so that it can remain in a defensible position against China.
Not that they have a mountain of shadow debt built upon the biggest housing bubble the world has ever seen (by far) and an absolute demographic time bomb about to blow up their future...
well, looking back at the Iraq WMD invasion - were US bogged down by democracy?
https://www.pewresearch.org/politics/2023/03/14/a-look-back-...
Take a look at the space around you. How many of the items you see were made in the US?
Your outlook is significantly more gloomy than reality