How should I interpret the following lyric from America:
we ain't had no time to drink that beer?
I don't think this is actually a double negative. For example, in French to say "I don't know", you say "je ne sais pas." Both the "ne" and the "pas" mean 'no' in a sense, but you have to use them together to convey the sense of 'no'. I think in this case, "ain't... no" is a similar construction. And it just means "no" or "didn't", etc.
The double negative in slang is generally redundant, i.e. it is a single negation.
"We aint had no time" actually means "We aint had time"
A double negative doesn't occur when no two forms of non-negation aren't not used in no not-same unsentence. Not in no languages no non-double unnegative doesn't resolve not to a non-negative, while in no others it doesn't not resolve to no not-positive.
... and so on :)