Bought iPad & Apps in New Zealand. Now live in the USA so can't update apps or buy new apps.

Bought iPad in New Zealand and downloaded Apps when living their. But have moved to the USA for twelve months. I can't update my Apps or buy new Apps. Error message states account not valid for US store so must switch to NZ store. But I can't do the latter because I'm in the USA. I can't successfully change to a US account via Settings. A solution could be to open a US account using another email address. But Apple Support don't recommend having two accounts ie one for NZ and one for USA. Will there be any issues have an coconut in NZ and another in USA?