Probably the broken up plan to do a mass bombing at one of her concerts already had them worried.
16 states and DC allow undocumented immigrants to get a driver’s license. I’m not sure how easy it is to obtain, but it is possible.
https://www.ncsl.org/immigration/states-offering-drivers-licenses-to-immigrants
Trump’s making merch similar to Taylor’s, just as the Harris campaign is doing. Of course, Trump doesn’t have her endorsement.
Even in most of those states, though, there’s the option of getting a RealID license, which does involve proof of citizenship.
In Washington, voter registration is only offered to those who get an Enhanced (Real) DL or ID.