I do not have this problem in the US. Not only does American food packaging have labels for various common allergens North Carolina just us Tar Heels shirt. There also labels for all manner of culinary preferences and diets available such as kosher, halal, organic, non-GMO, gluten-free, etc. Even the cheapest American buffets will have separate utensils for each dish so that allergens do not spread. Taiwanese are generally mindful of allergies and diets but many buffets still give you only one utensil to load up your plates from all the dishes. I have good friends with deadly peanut allergies so I am mortified to see everyone load up their plates with peanuts and then dig into the bok choy with the same scoop. Similarly, when I go to restaurants with Muslim friends in Taiwan, I have tried to explain that this person doesn’t eat pork. Many times, the dish will still have pork and when I tell the owner, they will say “oh our restaurant is very clean and the pork is very good quality.
No matter how ridiculous or non-scientific your chosen diet is, Americans will generally respect it and will not push you to eat what you don’t want to eat. Especially on the West Coast. Especially in Northern California. You could be raw vegan, paleo, Atkins, keto, pescatarian, nutritarian, Halal, Kosher, Hindu, Jain, Mahayana Buddhist, Seventh Day Adventist, fasting-for-Ramadan/Yom Kippur, caffeine-free, a teetotaler, intermittent fasting, high-carb, low-carb, no-carb, gluten-free, allergic-to-everything or “I only eat hunted meat” and people will generally let you be. Yes, some Americans will make annoying or ignorant comments, but it is rare to pressure someone to eat something they don’t want to. In places such as Portland or San Francisco, they may even go out of their way to cook dishes that are appropriate for you. I grew up as a Buddhist vegetarian and was active in the Boy Scouts in Oregon.