Any reasonable substantive analysis of the situation can't possibly limit itself to just the direct benefits of "having Denmark in our camp", especially considering the context of this thread. Would having the support of Denmark be the make or break factor in a war between the US and China? Almost certainly no. Would the second and third order effects of the US ending its alliance with Denmark and/or NATO, and potentially turning them into enemies, by forcibly taking over Danish territory or something similar impact the US ability to fight a war with China? Almost certainly yes.