TLDR For non-US context: she's been nominated for a bunch of Grammies for country music, so she's presumably talented and people in the US know who she is.
Her performance is being called the new worst of all time (something people have ridiculed Fergie for since her performance in 2018, because they care about national anthems over there) but now she's in rehab for alcoholism, so that explains it.
For reference, 1 litre of ice cream has about 180g of sugar in it. This milkshake is approx 0.95L and 263g, so 1.54x more sugar than straight ice cream.
(I wouldn't recommend eating a litre of ice cream all in one go either)