Is "I just spent all my money" grammatically incorrect? [duplicate]

American English tends to use the past tense in places where British English uses the present perfect construction, and this may be one such place. But in any case, the lyrics of popular music are not always written in Standard English and will consequently conform to a different set of grammatical rules.

Either one works. Anything that happened in the past can usually be expressed in the past tense.

If it's important in some way that the past event(s) are over and done with, or for some other reasons, the Perfect construction can also be used. But it's rarely necessary, except for emphasis and in idioms and fixed phrases like have got, have gotten, and have been to.