Bleached hair is more porous than unbleached hair. It loses some of its disulfide bonds to breakage during bleaching (those bonds are more abundant in curly hair and tend not to form in straight hair) and subsequent coloring. Breakage of disulfide bonds is how hair is relaxed.
If you have permanently colored and/or bleached hair, it is more susceptible to breakage, swelling and cuticle damage. It is possible that these processes can alter your curl pattern if your hair is fragile, or if a great deal of damage occurs.