AMD also had alot of those major bugs, but it wasn't reported as much since the original papers all targeted intel CPU's since they are the "standard", and then a couple months later someone would do it for AMD but it was old news.
All of the attacks are relevant in any environment where you execute code that you would rather not have access to any other information on your system (i.e. where you actually care about privileges).
For example, there have been demos of spectre in-browser, but applies to multi-user environments or simply apps that you didn't grant admin privs...
If you treat your computer security in a DOS/Win95 fashion, then none of them are relevant.
AMD CPUs were vulnerable to fewer of the speculative execution bugs than Intel, and the performance impact of the mitigations on AMD CPUs were far less than Intel.
