The thing to ‘get’ about underdetermination in the sense of a weak naturalism is that it is the condition for overdetermination in the sense of a particular historical social formation ‘setting the agenda’ from many directions.
One could well say that the constitutive weakness of any state of nature opens the space for something like a State (as a stratified system of relations, of course). It is precisely because we are ‘free’ (not fully constituted ontologically) that we are so exposed to historical constitution, to determining forces.
History burdens us because there is a hole where ‘Nature’ forgot to be that providential guarantor of universal consistency that scientific naturalism so often mistakes her for. This lack is bombarded by forces that attempt to cover over it with myriad ideological accounts, over-determining a particular historical form.