Was Texas's Lawsuit an Attack on State Rights?
The answer is no.
The progressive media - desperate to attack conservatives in any way they can - have denounced Texas v Pennsylvania et al. as a shameless attack on states' rights. Pretending this lawsuit is an attack on the individual sovereignty of states simply continues their ceaseless and tiresome claim that Donald Trump is a dictator and the GOP are his lackeys. (Frankly, not a single member of the GOP elite has the spine to be anyone's lackey, let alone Trump's.)
Breaking down the progressive claim, it is reasoned that because Texas is asking the Supreme Court to nullify the election results in other states, Texas is unfairly meddling in another states internal business. If the significant pieces of Texas's claim is ignored, the progressives' claim is valid. Generally, Texas or any other state has the right to determine how their own elections are run. Individual states are responsible for determining everything including the requirements for a candidate to appear on the ballot, the methodology of how ballots are distributed and tabulated, and, to an extent, the eligibility of voters. Before the 2020 election, the courts and officials in Pennsylvania et al. decided to enact changes to their respective election processes so their residents can be protected from COVID-19. Texas generally should not have standing to challenge these changes.
The Texan claim, however, calls into question the methodology the states used to change their election process, rather than the process changes themselves. Although this is a subtle difference - and indeed the end result would surely be the same - it is a difference which should have given Texas standing in their lawsuit. The Electors Clause of the United States Constitution gives the individual State legislatures plenary power in deciding how electors for that state are chosen. Further, the Supremacy Clause of the Constitution would cause any state executive action, state court ruling, or even state constitution that runs afoul of the Electors Clause to be considered null and void.
In its lawsuit, Texas is claiming Pennsylvania et al. violated the Electors Clause by altering their election process without the approval of the various state legislatures as the Constitution requires.
Returning to the question at hand, is Texas's lawsuit an attack on the rights of other states? No, because Texas is claiming the actions taken by Pennsylvania et al. were forbidden under the US Constitution. Individual state executives and courts do not and never had the right to arbitrarily change their state's election process without the consent of the respective state legislature. Any claims an individual state could make to this right would have been surrendered upon the state entering the Union.
Texas's lawsuit was an attempt to ensure Pennsylvania et al. were following the supreme law of the land, which is something wholly different from an attack on state rights.