、。
All I can really do is wonder if everyone else feels the same way.
Literal
Everyone too so [explanatory-no-question-のかな], [quotative-と] think thing about-only-くらい can-do-not.
A complex stack of nested structures. みんなもそうなのかな is an internal monologue ('I wonder if everyone is like that too'), framed by the self-questioning ~のかな. It's then quoted by と思う ('think that...'), nominalized by こと ('the thing of thinking that...'), restricted by くらい ('about that much / something like that') and しか ('only'), and finally negated by できない ('can't do [more than that]'). The whole construction conveys helpless resignation: 'wondering is all I'm able to do.'