You can't really compare the two tbh, and I don't mean in terms of the respective financial dealings of Rangers and Manchester United.
There exists a totally different culture around non-senior football in England, both in terms of their involvement in the FA Cup and the overall league pyramid. Fine, I'm sure there are a lot of Clydebank fans who still love going to watch their team play, and get a great enjoyment out of their efforts - but non-league football in Scotland is treated as this pathetic sideshow, rather than a smaller part of the big picture.
That's not to say that FCUM supporters have the ultimate aim of seeing their club get promoted to the football league, but you can't deny that the presence of that possibility is a bit more tempting than its absence.