句子的主干:It's as if they were cosmic beings.
这是一个主系表句型:It(主语)+ is(系动词)+(表语从句)as if they were in some sense cosmic beings in violent and lovely contrast with us suburban creatures.
在表语从句中,as if是引导表语从句的连词;
they were cosmic beings是表从的主干,也是一个主系表结构;
in some sense是状语;
in violent and lovely contrast with us suburban creatures是介短作定语,修饰cosmic beings;
其中,in contrast with是一个固定短语,violent and lovely是作定语,修饰contrast; 句末的suburban creatures是us的同位语.
句意:从某种意义上讲,他们似乎是宇宙人,同我们这些凡夫俗子形成了强烈而鲜明的对照.