I experienced this when traveling Thailand; it was nearly impossible to get food that was spicy enough to match my Atlanta, Georgia (US) expectations. The staff would snicker as they brought the chili's out.
In many ways it made me realize just how good multiple cultures have combined to make my "home" food good.
Food in Thailand is often not that spicy by default. The condiments on the table are what allow everyone to adjust the spiciness to their preferred level. So, I wouldn't say it's necessarily the staff thinking you can't handle it, it might just be how the dishes are always prepared.
As a Thai person, the cooks know that if they have non Thai guests, especially "Farangs", they need to tone down their spicyness. You have to insist them or bring a local to have them make it hot.
In many ways it made me realize just how good multiple cultures have combined to make my "home" food good.