I have MSVS 2010 on my system (x64, Win7), and this is the only version of MSVS I have installed. I just installed CUDA 7.5. I chose the local installer at the download prompt. The installation went without a hitch, the installer successfully integrated CUDA 7.5 and NSight into my existing MSVS 2010 installation.
So it is not clear what the problems are in your case. Since NVIDIA cannot test the installation process against any possible configuration variant of MSVS, I could imagine two potential issues: (1) MSVS is not installed in default locations (2) country-specific version of MSVS. However from one data point it is not possible to identify either of those as the problem, that would require multiple users hitting the same snag.
For better or worse, CUDA requires tight integration with the host compiler. The practical constraints of that approach (limited engineering resources) make it necessary to limit qualifying this integration only with the most frequently used host compilers for a given platform. On Windows, MSVS is by far the predominant tool chain.
Since there are people like me who still use old versions of MSVS, while others (including CUDA users in this forum) are clamoring for support of the latest version MSVS, NVIDIA uses a sliding window approach where periodically support for old versions of MSVS is discontinued and support for new versions is added. The covered span of compilers stretches across five years on average. CUDA 7.5 will be the last version to support MSVS 2010, as this is marked deprecated in the release notes.