I am sure there are some people in Pennsylvania who raise Texas Longhorns. But I am sure it is not correct to say that Texas Longhorns are very popular in Pennsylvania.
I live in Texas, where there are probably more Longhorn cattle than anywhere else, and I would not say they are very popular here in Texas. I can name many other cattle breeds that are more common than Texas Longhorns here in Texas.
That being said, I think crossing Texas Longhorns and Angus makes for very hardy momma cows that are easy keepers. I would put a continental bull on those cows and sell the calves.
Bullit, I think you hit the nail on the head with the "Hardy and easy keepers" piece. These cows are gentle as heck around people (they come running and want me to scratch them), hell on 4 feet to any dog or predator within eyesight of the pasture, good milkers, great mamas, and so far giving good gain to nice looking black calves that will be able to finish nicely on grass alone if I wanted. We'll see what I get in the fall, but I can't really imagine I'm going to take a hit with how these calves look. I'm half considering getting a natural beef cert and when I get a little bigger selling to JBS 5 rivers or someone like that as natural grass fed Angus. They more than meet the requirements from what I can tell.