Syntax maker can automatically pick the right case for place names when you use them through the add_advlp_to_vp method. The possible values for place_type are in, to and from depending on the directionality of the movement with respect to the place name.

vp = create_copula_phrase()
subject = create_phrase("NP", "koira", {"PERS": "3", "NUM": "SG"})
predicative = create_phrase("NP", "Venäjä")
vp.components["subject"] = subject
add_advlp_to_vp(vp, predicative, place_type="in")
print(vp)
>>koira on Venäjällä