In the fifteen years between Texas' admission and secession there were four presidential terms - 3 Democrat and 1 Whig. There were six Secretaries of War - 5 southerners and one from the north. If Texas had issues with how the government allocated resources then wouldn't their complaint be directed towards Democrat administrations and Southern cabinet members?
Read Texas' declaration of causes. It states in relevant part:
"The Federal Government, while but partially under the control of these our unnatural and sectional enemies, has for years almost entirely failed to protect the lives and property of the people of Texas against the Indian savages on our border, and more recently against the murderous forays of banditti from the neighboring territory of Mexico; and when our State government has expended large amounts for such purpose, the Federal Government has refuse reimbursement therefor, thus rendering our condition more insecure and harassing than it was during the existence of the Republic of Texas."
They have impoverished the slave-holding States by unequal and partial legislation, thereby enriching themselves by draining our substance.
They have refused to vote appropriations for protecting Texas against ruthless savages, for the sole reason that she is a slave-holding State.
Note how similar a lot of those complaints are to today. The federal government goes out of its way to screw over Red states in ways both small and large - be it threatening them for election integrity laws or protecting parents' rights against trans indoctrination of their children in school or banning life altering drugs or surgeries for children without their parents' consent or simply for not taking away their citizens' right to live freely from Covid tyranny, because the Democrats view them as domestic enemies. They've even been so nasty and vindictive as to deny treatments for Covid positive patients in those states. The same kind of nastiness and vindictiveness was in evidence 150+ years ago from those who controlled the federal government.