Finding soy milk in the States isn't very difficult - it's generally stocked in supermarkets and used as an alternative to dairy. However, I'm not sure if the flavour of typical American soy milk (even the "unsweetened" variety) is sufficiently similar in taste to the soy milk I've had in East Asia.
As an example - in Hong Kong, if I remember correctly, Vitasoy sells unsweetened soy milk with the ingredients listed as:
Water, soy beans
Comparatively, the Silk brand that sells non-dairy alternatives lists additional ingredients on their soy milk (even the "original" variety or the "unsweetened" one), such as additional vitamins and sea salt.
Is the soy milk commonly sold in supermarkets in the US (outside of places such as Asian supermarkets) similar in taste to the type found in East Asia? I've heard that there might be some differences, but I don't have enough "experience" with this to judge if those accounts are correct.