"You mean those immigrants from Mexico that have a far higher vaccination rate than the US?"
Because vaccination often wears off and isn't 100% effective, many measles cases are among vaccinated people. The far more serious Ukraine measles epidemic, with ~20x the cases in 1/7th the population, directly followed a measles vaccination campaign where the 2nd-dose vaccinated proportion of 6-year-olds tripled in a year, from 31% to 95% 2016-2017. The MMR vaccination was not only ineffective, it quite likely caused the epidemic.
"It has been proven over and over..."
Liar. It's not just illegal immigrants, to be sure - legal immigrants are also spreading epidemics.
Summary of CDC report: "2018: The U.S. experienced 17 outbreaks in 2018. Three outbreaks in New York state. New York City, and New Jersey, respectively, contributed to most of the cases. Cases in New York and New Jersey occurred primarily among unvaccinated people in Orthodox Jewish communities. These outbreaks were associated with travelers who brought measles back from Israel, where a large outbreak is occurring. Eighty-two people brought measles to the U.S. from other countries in 2018."
The current outbreaks are in Arizona, California, Colorado, Connecticut, Florida, Georgia, Illinois, Indiana, Kentucky, Maryland, Massachusetts, Michigan, Missouri, Nevada, New Hampshire, New Jersey, New York, Oregon, Texas, and Washington. These are all high immigration states, legal and illegal. 2014 had 3x the cases of any other year from 2010-2017, and the source of the outbreak was the Philippines. 75 of 2017's 120 cases came from a single outbreak among Somalis.
Immigrants to the US from 3rd world countries spread epidemic disease beyond doubt, no epidemiologist will deny it - in fact they are the main source, travelers being the other and far less frequent origin of epidemics.