Useful links for Portulaca ID.

Portulaca in the USA:
Flora of North America, Portulaca: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=126612
In the Southeast: Matthews, James F., and Patricia A. Levins. "The genus Portulaca in the southeastern United States." Castanea (1985): 96-104. https://www.jstor.org/stable/4033134

Portulaca in Argentina:
http://buscador.floraargentina.edu.ar/species/search?genderName=portulaca&speciesName=

Portulaca in Brazil: 13 species are found there.
Coelho, Alexa Araujo de Oliveira Paes, and Ana Maria Giulietti. "O gênero Portulaca L.(Portulacaceae) no Brasil." Acta Botanica Brasilica 24 (2010): 655-670. https://doi.org/10.1590/S0102-33062010000300009

Portulaca in Cuba:
García-Beltrán, José Angel, Duniel Barrios, and Y. Eldis R. Bécquer. "Revisión taxonómica de Portulacaceae en Cuba." Brittonia 73, no. 3 (2021): 274-303.

Portulaca in Mexico:
https://www.inaturalist.org/posts/27133-portulaca-mexicana-y-p-pilosa
Checklist of the native vascular plants of Mexico: There are 14 species of Portulaca native to Mexico: *P. californica D.Legrand, P. conzattii P.Wilson, P. grandiflora Hook., *P. guanajuatensis G.Ocampo, P. halimoides L., *P. johnstonii Henr., *P. matthewsii G.Ocampo, P. mexicana P.Wilson, P. oleracea L., P. pilosa L., P. rubricaulis Kunth, *P. rzedowskiana G.Ocampo, P. suffrutescens Engelm., P. umbraticola Kunth. Species with * are endemic. https://revista.ib.unam.mx/index.php/bio/article/view/1638/1296
Weeds of Mexico site: http://www.conabio.gob.mx/malezasdemexico/2inicio/home-malezas-mexico.htm
Flora de Veracruz, Portulacaceae: (P. grandiflora, P. oleracea, P. pilosa, P. umbracticola) http://www1.inecol.edu.mx/publicaciones/resumeness/FLOVER/51-Ford.pdf
Portulaca in the Yucatan: (P. halimoides, P. oleracea, P. pilosa, P. rubricaulis ) https://www.cicy.mx/sitios/flora%20digital/indice_tax_especies.php?genero=Portulaca
Portulaca juliomartinezii sp. nov.: Ocampo, Gilberto. "A new perennial species of Portulaca (Portulacaceae) from central Mexico." Phytotaxa 347.1 (2018): 89-95.
https://doi.org/10.11646/phytotaxa.347.1.6