USA swimming ??

Does membership with USA Swimming (not USMS) require any sort of attachment to a specific club? Or, in other words, can I join USAS and go swim whatever meets they have as an "unattached" swimmer. The master's program I swim with only had USMS affiliation. On a similar note, do times achieved in a USMS meet have any sort of merrit for making Q times for something like a Grand Prix meet?