No, the US is less than 65% Christian.
I was thinking about your question and did a little digging and since you seem to be focused mostly on the US here are some comparisons. As you can see from the handful of comparisons I found, it would seem that atheism is more prevalent in primarily Orthodox countries than in the US. Perhaps other surveys paint a different picture or maybe there are more up-to-date surveys that can be found. I would also suspect that there are other countries where atheism is less prevalent than in the US but these that I have referenced do not appear to be as you have asserted.
US
Percent of population identifying as Christian is 67% latest data (source: PEW Research Center)
Percent of population identifying as atheist is 4% 2023 data (source: PEW Research Center)
Russia
Percent of population identifying as Christian is 68% 2025 data (source: Russian Public Opinion Research Center)
Percent of population identifying as atheist is 14% 2021 data (source: All-Russia Center for the Study of Public Opinion)
Greece
Christian 81%-90% 2022 (source: US Dept. of State, various polls)
Atheist 4%-15% 2022 (source: US Dept. of State, various polls)
Bulgaria
Christian 65% official 2021 census
Atheist or no religious affiliation 5%, would or could not define 7% official 2021 Census
edit: I also found this interesting. I see you're from the UK so I dug into that a little too.
Percent of UK citizens identifying as Christian according to a 2021 census was 46.2% while 45% identified as atheist or non-religious. By this report, it would appear that the UK is a world leader when it comes to atheism.