I just did a Google search and clicked upon the first result:
Here it shows the US as a Cancer.
US is definitely a Cancer, just consider the fact that only around 35 percent of US citizens have passports and travel abroad. But yes, I hear you, people commonly think that US is Gemini, maybe because strong Mercury in the chart and the fact that chattiness and trade are so important to the US. Here even astrotheme.com believes US is Gemini (and I don’t know what it’s based on)
‘Some traditional associations with Gemini: Countries: Belgium, Wales, United-States, Lower Egypt, Sardinia, Armenia. Cities: London, Plymouth, Cardiff, Melbourne, San Francisco, Nuremberg, Bruges, Versailles.’