You can use TOP :

Select TOP 1 Country, COUNT(EmployeeID) as [count]
from Employees
group by Country
order by [count] desc

Try this. qty - count for country, maxqty - max count for all country.

Select Country
  ,COUNT(EmployeeID) qty
  ,MAX(COUNT(EmployeeID))over() maxqty
from Employees 
group by Country

For test data

create table Employees (EmployeeId int,country varchar(20));
insert into Employees values 
 (1,'country1'),(2,'country1')
,(3,'country2'),(4,'country2'),(5,'country2')
;

Result