Math graduates is what most of the body of grad students in statistics is made up of (I've been both a stat student and a stat faculty, so have seen a fair number of these folks). In terms of getting into a program based on your credentials, you wouldn't have any issues (unless, of course, your US-style GPA is like 2.2, in which case you would have some explaining to do in any application to any program, no matter what the discipline is). If anything, you'd be better prepared to tackle the theoretical courses. For instance, the Central Limit Theorem should be proven using characteristic functions rather than moment generating functions, since the latter are not defined for all the distributions to which CLT applies; as a good math major, you probably have had a course in complex analysis. What's more, it might be easier for you to get to a top program, as lower ranked ones may consider you to be overqualified. On the other hand, as other answers strongly suggest, you need to have a more practical mindset than what is typically found among pure mathematicians to get through the applied courses. (The most difficult ones for me were the courses on psychological aspects of response in survey data collection: there was about 5 papers ~ 100 pages worth of reading every week, and the concepts were entirely foreign to me.)
Check out CrossValidated site in the SE system to see what this could be about. (Note that it is heavily biased towards computational/machine learning side of statistics.)