Single biggest problem is there is no LEGAL way for Texas to secede. The last time they did they actually had a legal right to do so, (the only state in the Union with that specifically written in the agreement that they joined the Union under) HOWEVER they were specifically forbidden from engaging in or supporting armed conflict with the United States which would abrogate the a fore mentioned agreement. Then they went and LOST that conflict which meant they had and have no legal rights to any of the a fore mentioned agreement as they themselves had broken the agreement.
I post it primary as a speculation not as a fact. Do you thing it is so unlikely?
Horribly unlikely as they would and do have far to many reasons to stay rather than go, rhetoric aside
Since when is being part of bigger union means better economy.
People like to point to Texas' economy but the truth is that get a LOT of Federal subsidies and benefits from being a "state" rather than a "nation" and to even have a chance at plausibility you have to come up with a valid reason why they would leave the Union and why the Union would allow it.
Not easy.
Most of the roads and highways are supported by Federal not state money, the National Guards are pretty much paid for and by more Federal than state money, (and the States WANT it that way) infrastructure costs are subsidized more by Federal that state and local money except in the most basic circumstances. And how does Texas go about paying back the Federal government for things like lands and past investments? Frankly most ""secessionists" don't bother to even consider such "trifles" for a very good reason
There wouldn't be any way* for the USA to let Texas secede? Even if there was a referendum and the people of Texas voted to secede?
Or is it that the USA would not allow such a vote to take place in the first place?
The (and there have been several over the years) petitions over the years have never come close to being "worrying" to the US government. The majority of Texans (and other states) residents don't buy into the rhetoric and fully understand they are better on in rather than out of the Union. (Fun fact: On most petitions that are NOT exclusively segregated to Texas residents people who are NOT Texan are the majority signatory's. Seems the idea of Texas leaving the Union is more popular OUTSIDE of Texas than within

)
Bottom line though is there is no legal way for such a referendum to be brought to a vote. Texas violated an agreement with the United States and as a result they lost the ability and right to leave the Union on any terms. The US for its part has no mechanism in place or suggested to be able to allow secession. It's a nice fantasy but short of dissolution of the Union itself, (which technically COULD happen but Texas would have to be one among many and really what's your "mechanism" to bring that about in any realistic sense?) Texas has no way to bring this about.
Randy