I don't know about Americans as in "person from the United States" [why on Earth don't you have a term for people from your country in English? Dictionaries remain mute. o.o], but Americans as in "person from America" here don't stare a lot. Since we both have a Western culture, it should be relatively similar in the US.
Well, quite a few will give a weird look or something if something is weird, but they won't actually stare at "weird" people. Only particularily rude people stare, usually. That, or if they're genuinely trying to understand what gender you are, which shouldn't happen in your case.
When confronted with something very weird or disrupting, I think most people actually avoid to look at it once they've seen it.
And also, as it's been said, 5'11 sure is well over the average woman's height, but women that tall actually exist in significant numbers here - I'd say about 5 % - so it's much less shocking than in some Asian countries where people, especially women, are typically very short compared to the Caucassian average, and even a tall man would get stared at a lot, right?
Finally, otherwise, you pass very well, I think. People -might- look at you, surprised to see such a large woman (even though you most probably won't be the first/tallest they see), but I don't think they'll clock you or give you a hateful look. Well, apart from envious aspiring models who were rejected because they were too short, maybe! Ehe.