When I learned about acid strength, i learned that the strength of an acid increases with it's degree of ionization when solvated. So, in water, a strong acid is one where $[H_3O^+]$ is large, which is equal to a low pH: $pH=-log[H_3O^+]$.

Considering extreme cases, such as superacids, I have found out that other methods are used to measure their acidity (Methods i don't really understand). My question is why is it impossible to simply get super high concentrations of $[H_3O^+]$ in aqueous solutions of superacids, and use this to determine the acid strength. Also, is pH used as a measure of acidity outside of aqueous solutions?

I have come over the leveling effect, but I don't think i fully understand it. The way i understand it(for the case with water as solvent) is that basically any acid in water will protolyze $H_2O$ to $H_3O^+$, making this the effective acid. I don't understand why this would affect the measured pH, as it is $[H_3O^+]$ you are measuring.

I learned about acid strength, that the strength of an acid increases with it's degree of ionization when solvated. So, in water, a strong acid is one where $\ce{[H_3O^+]}$ is large, which is equal to a low pH: $\mathrm{pH=-log[H_3O^+]}$.

Considering extreme cases, such as superacids, I have found out that other methods are used to measure their acidity (methods I don't really understand). My question is why is it impossible to simply get super high concentrations of $\ce{[H_3O^+]}$ in aqueous solutions of superacids, and use this to determine the acid strength. Also, is pH used as a measure of acidity outside of aqueous solutions?

I have come over the leveling effect, but I don't think I fully understand it. The way I understand it  (for the case with water as solvent) is that basically any acid in water will protolyze $\ce{H2O}$ to $\ce{H3O+}$, making this the effective acid. I don't understand why this would affect the measured pH, as it is $\ce{[H_3O^+]}$ you are measuring.