NZ Navy

Hey there, I am new to this site but I seem to notice that it is geared towards an American audience. My question to those in the US military is this-if I were to join another nation's military (New Zealand Navy to be precise) would I suffer any kind of consequence from the United States? I am a 17 year old American citizen living in New Zealand and I just want to know what the ramifications of me doing this could be. Any help would be appreciated.