Q: Why does Welcome to the Black Parade sound like blink-182?
A: because the artist(s) have heard blink-182 before. Or, sometimes there is an alternate phenomenon where both those 2 artists were actually influenced by a 3rd artist before both of them. but in this case i think there are many many artists who have had the sound you are refering to. blink-182 being maybe the one you think of most readily because they are perhaps the most famous