Contact your recruiter immediately. They are professional negotiators. HR have acted out of turn by contacting you. It may well be that they have another candidate who asked for less money and they're now giving you the option to lower your expectations to be considered. But it could also be some dirty HR tactic to lowball you.
This says a lot about the company and frankly I wouldn't want to work for them if they're only looking to hire the cheapest person they can find.
Should I contact the country head about this change prior to the call with HR, or wait until I hear back about the next round of interviews?
Sorry to say it but NO. Despite the country head offering you a particular salary they have now passed this hiring process down to HR.
If you go over HRs head at this point the likely results will be:
You'll not be invited to final interview
If you do get the job you will be on HRs bad side from day one