It is not weird if you were old enough to be aware of the news during that time. Poor people in the US suddenly coming into money and being lifted out of poverty thanks to COVID stimulus checks was front and center in the news cycle as it was happening. The other countries noted did not follow the same "hand out free money" approach. Their safety nets were built around maintaining continuity during COVID.
1) That all of the effects of America's wealth inequality on American poverty could be made up for simply by giving everyone a thousand dollars a year. Not even UBI proponents are that optimistic.
2) That nothing any of the 3 comparative countries did or did not do during a massive global pandemic did anything to alter the relative poverty levels of their populations in the slightest
3) That the major economic crashes and recessions over the last few decades have actually improved American average poverty (notice that the US rate dips for the beginnings of the dot com crash, 9/11 and the 2008 financial crisis, despite none of those coming with government stimulus checks.
This measurement might be have something interesting to say, but I'm not sure it's saying what is being claimed. It feels more like they've found a more volatile measure of the US economy and stock market than of poverty.
A lot was written about the stimulus checks but they were so small to not matter. A $1200 check isn't going to suddenly lift a lot of people out of poverty and keep them there, even though it could be make-or-break for a few selected cases.
The bigger change was that the American economy was basically turbocharged by all of the interventions going on. Remember "The Great Resignation" when everyone was changing jobs because all the companies were hiring as fast as they could? It was an ideal time to move your way into a better position in the job market.
"A lot" is subjective, I suppose. Concretely, it lifted 11.7 million Americans[1] out of poverty. That makes up approximately 30% of those who were in poverty prior to the stimulus.
[1] https://www.commondreams.org/news/2021/09/14/incredible-covi...
A lot of things changed during that time, notably the job market. Getting a new job that paid $1/hour more would be more impactful than a $1200 stimulus check. People were getting raises much bigger than that.
The checks were not the primary driver of the economic changes
The article doesn't do anything other than quote the US Census Bureau.
Obviously you will have already read the citation in full, but for everyone else here is the full quote: "Stimulus payments, enacted as part of economic relief legislation related to the COVID-19 pandemic, moved 11.7 million individuals out of poverty. Unemployment insurance benefits, also expanded during 2020, prevented 5.5 million individuals from falling into poverty."
Again, this is from the US Census Bureau. It is being asserted in an official government capacity, from an governmental organization that has access to all the relevant data. If you think that they got something wrong you're going to have to offer something more compelling than some random theory you made up on the spot.
This one needs a little common sense. A one-time $1200 stimulus check is not going to lift 11.7 million individuals out of poverty in any meaningful sense, unless you're literally just looking at people within $1200 of an arbitrary cutoff and saying you "lifted them out of poverty" by bumping them over that threshold for the year.