That's a problem with pre-spooled reels. The line has been tightly wound on a small arbor and probably been sitting for some time and has developed a tight coil memory. Stren is decent line but under those conditions I suspect most mono would do the same thing.
I fish a private pond for Bluegill and Crappie but I've lost lures to 4-5#Largemouth so I've switched to 6# Fireline braid with a 6# mono leader. I can cast light jigs and small Beetle Spins with ease using the braid and I've landed several nice bass too.
The 6# braid has a tiny diameter, probably like 2-3# mono, it has no memory and cast really well.
Just my preference, I'm sure there are several other viable options.