I never paid attention to the word until I came to Kbin and subsequently Lemmy.

https://en.wikipedia.org/wiki/Tankie says:

Tankie originated in the UK as a term for hardline members of the Communist Party of Great Britain (CPGB) who continued to pledge support for the Soviet Union even when doubts had begun to emerge elsewhere in the party.

... Politically speaking, tankies regard past and current socialist systems as legitimate attempts at creating communism, and thus have not distanced themselves from Stalin, China, etc.

Practically speaking, tankies are pro-fascist and pro-genocide, plus individual (literal) murders, so long as it is done by their favored in-groups (e.g. Russian aggression vs. Ukraine portrayed instead as poor whittle russia forced to defend itself, whoopsie), and opposed to anything (even outright socialism) when done by their opposed out-groups - chiefly Western Civilization.

So their cries of "Death to the USA" are meant literally, and also inclusive of other NATO states.

Source: go visit Lemmy.ml, which unlike most other instances by default without being logged in shows only Local rather than Global content, and see for yourself, it should only take a couple of minutes to find such evidence. Or possibly better yet lemmygrad.ml, except that most instances actually defederate from that one whereas almost none defederate from Lemmy.ml.