the reason 'I am Japanese' doesn't cut much ice.
Grasshopper, you still have much to learn.
There is no victory in this game. This is not a legal case to be won or lost. The reason is valid for her.
Even if you could find a web-site that said it was unnecessary to perform a ritual cleansing of the house, her response would be the same. Even if your Japanese skills were rock-solid and you could argue the logic of your case super-eloquently in Japanese, the result would be the same. This is beyond logic, and its just something she wants to do regardless of what you think about it.
So, since she is the woman you swore to uphold, protect, for richer or poorer, etc... there is no need to try to prove yourself right or wrong here, there is only a need to not be a cranky thorn in your wife's side.
I found a site where people are arguing the merits of this kind of thing, and the results are as one might expect; some people say it isn't necessary, while others say they would absolutely do it.
新居への引越しにお祓いは必要だと思いますか? - アンケート | 【OKWave】
A shinto website that provides this service (and charges 20,000 to 30,000 for it).
家のお祓いについて
Congratulations on the house. May it bring you both much happiness.