Reg on the side...........?
I think you will find most aviation authorities will allow the aircraft to be flown as follows.........
1/ Your licence matches the tail tag regardless of where you are.
2/ You can fly most aircraft if your licence is valid in the country where you happen to be, for that aircraft, regardless of the tail tag. USA, NZ, AUS, JARLAND.
i.e you have an AUS licence, you are in AUS you can fly an N tagged aircraft without a US licence. FAR 61.3 (1)
Now that does not mean to say you could fly a N tagged aircraft in AUS on a Canadian licence although you probably could in Canada obviously.
The same philosophy applies with maintenance as well. But look it up as the case may be as there are exceptions.