Texas (and BA, FL, NC) are in play because Republican policies have been successful. Voters from Rust Belt cities are migrating to Red state jobs.
Nobody (at least in GA) is asking these new voters why there are no jobs in Democrat Rust Belt cities and plenty of jobs in Red states. The Republican Party (RNC, State and County) are not asking. Heritage, CATO, AFP are not reaching out beyond the choir. Tea Party and Trump supporters are all focused on the non-voters coming from outside the US.
Non-citizens are not the threat. Rust Belt voters who don’t undestand why they are in Red States need to be educated. Nobody is providing the service.
How much of Rust Belt workers migration to southern states is because of “right to work” laws. Meaning that businesses relocate in the south because they no longer have to contend with unions demanding better pay for their workers who in non right to work states have to support the union whether they like it or not to get this better pay that drives the bosses south.