Here is some background on illegals voting in US elections
https://www.investors.com/politics/editorials/trump-is-right-millions-of-illegals-probably-did-vote-in-2016/
https://archive.fo/p2Que
https://www.sciencedirect.com/science/article/pii/S0261379414000973
https://archive.fo/QvFPP
https://ww2.odu.edu/~jrichman/NonCitizenVote.pdf #<- paper referenced in sciencedirect URL
https://archive.fo/OyJvi