isn't the first syllable stress in Góral speech not influenced by Czech and Slovak?
No, you're getting too hung up on state borders. What happens is that as you move south from Wrocław, Częstochowa, Kraków the penultimate stress in words eventually turns into initial stress.
On the other hand if you're moving north from Liberec, Olomon and Presov, then the initial accent eventually turns into penultimate accent. In other words, there are two accent areas in western Slavic, a penultimate one that's north of an initial one and the border is porous. It roughly corresponds to national borders, but not entirely so that you find some initial stress in Polish areas near the initial stress zone and (somewhat less commonly) penultimate stress in northern areas if the initial stress zone. There's really no point in talking about one 'influencing' the other.
In rough, simplified terms, look at the block below (where P = penultimate and I = initial)
You'll find you can't draw a border (in a straight line) that includes all the P's on one side and all the I's on the other. That's the way to think about fact that the stress borders (and standardized national linguistic borders) don't exactly coincide.