Looks like Mimosa pigra. Whereabouts is it? It's a very bad weed and should be reported. If it's already a small tree it could have been shedding seed for quite a while.

My Plantsnap app doesn't recognize it but having grown up in the south I would say Mimosa also - the leaves are pinnate and the flower stalk looks very much like a Mimosa.

It is a species of Acacia or wattle. But there are a fair number of species that have globose flower structures like that and my familiarity with them is just passing :-)

It would help to see it actually in flower rather than just budded and with a single spent blossom. They bloom both yellow and white.

Sample photo: (this one happens to be Acacia guinettii)

See if Vachellia farnesiana is a match. https://keyserver.lucidcentral.org/weeds/data/media/Html/vachellia_farnesiana.htm

^^ Synonym: Acacia farnesiana

Yes. Not in dispute.