Nonsense! First, if PA had a case against TX, that would be a separate case, not something that would somehow negate the TX claim. Second, the TX claim is that PA’s violation (and those of the other 3 defendant states) of it’s own law had a sufficient enough effect to change the results of the single national election that we have under the Constitution. It is beyond absurd to claim that a single ballot violation of TX law had such an effect. You’re really reaching here.
1. Look up the term "Entire Controversy Doctrine." It's a principle of common law that requires the parties in a legal dispute to assert ANY claims related to the underlying matter between them in the same case. This is why almost every civil lawsuit I've been involved in (mostly in a professional capacity) included counterclaims that had little or no basis in fact but had to be filed in order for the defendant to protect their rights under the Entire Controversy Doctrine. If you are a defendant in a lawsuit and you don't file a counterclaim in your initial response, it's rare for a court to let you amend you filings and file a claim later.
2. Then look up the "Unclean Hands Doctrine." Again, it's based in English Common Law and applies to situations where the plaintiff in the lawsuit is trying to sue defendants over something that the plaintiff is guilty of practicing itself. If your business partner defrauds you in a business matter, for example, you can't sue him for damages if he can prove that you had also defrauded him in the same business relationship. A plaintiff who has "unclean hands" is barred from pursuing claims for the same matter in a court of law.
These two items explain why Pennsylvania (and the other three states) would have immediately asserted counterclaims against Texas if the case had been allowed to proceed.
By the standards of Texas’s own argument in its lawsuit, Texas had about half a million illegal ballots cast in Harris County alone. They were illegal because they were cast in violation of the manner directed by the legislature, and because some of them, by Texas’s argument, also violated Equal Protection. So if Pennsylvania’s election must be voided, then so must Texas’s on a counterclaim by Pennsylvania (if either state had standing, which they do not).
Some better info: In Harris County, about 628,000 in-person votes were cast before the time for early voting as authorized by the Texas legislature. I don’t have the numbers for the full period state-wide, but 2.63 million voted state wide between 10/13 and 10/15, and I’m pretty sure at least another million voted by 10/18. The first date for early voting as authorized by the legislature was 10/19. Trump’s margin state-wide was about 631,000, barely more than the number of illegal early votes cast in Harris County alone (and that does NOT count the also-illegal drive-through votes, at least 127,000, cast in Harris County).
I can tell you that based on what I’ve directly observed of early-vote counting, I am pretty sure we cannot segregate the illegal pre-10/19 votes from the legal early votes. It is absolutely possible that invalidating those pre-10/19 votes would have swung Texas to Biden.