Can we trust nutrition facts about food packages?

If printed in the USA, ~100% of the time, yes. But keep in mind, these are almost always averages. One particular can of sweet potatoes may contain slightly more or less than another. Do what I do and use a digital food scale. An immensely valuable database is nutritiondata.com .

If printed in countries that use different alphabets (China, Taiwan, Japan) nutrition info is spottily unreliable.