I measure by number of months I can keep doing whatever I'm doing with zero income. That is, if all of my clients cancelled on the same day and refused to pay me anything they owe.
Six months is what I like to have. Two months makes me uncomfortable.
Try doing what most americans do, and don't tell them which country you're from. Instead give a local answer. "I'm from California," "I'm from New Orleans," etc.
Then if they ask where that is, say that it's in the US.
Once, to an apartment manager, when I was taking over an abandoned lease and needed to give her a "fits in the box" sort of answer about my source of income and why I wanted to assume a lease so near its end-date.
"I do many things depending on what my clients need, from web design to Excel back-end work to odd programming jobs but it varies," wasn't the sort of answer I think she wanted to hear.
The area I was born in.
I imagine that will probably be true for most people.