International bandwidth is much more complicated than this, with respect to a p2p network such as Bitcoin. Much like bittorrent, the bandwidth for Singapore is functionally replicated for all of the Bitcoin clients in all of Singapore, so it's not true that the international connection is divided among the many peers all trying to download the same block, it's effectively shared data as if there were a locally available seed on Bittorrent. Granted, it's not the same as saying that all of Singapore could be regarded as one node, and then the block replicates across the entire nation-state from one copy; but once one copy of the block has made it across the bottleneck, the local bandwidth effectively becomes the limiting factor to propagation.
Sure but you would be slower by atleast the time taken by the fastest node in your country. To mine profitably, you would want to be well connected with all other mining nodes worldwide, so international bandwidth matters a great deal. Getting information 2nd hand potentially doubles your network overhead timewise.
A serious miner would want to have as much upstream bandwidth as possible to get his block out to as many relay nodes as fast as possible, so the upstream requirements should ideally match the download requirements.
Ofcourse i believe some of these issues can be optimised.
For example you could request a block with only the hashes of the TX it contains, and you use the transactions in your not-included TX pool instead of downloading them. For your average transaction this wont help much, but for transactions with many inputs and outputs, this could help reduce burst BW requirements significantly.
The more i think of it, the more it seems to me that even at 10MB, most residential miners without an expensive connection will be out of the game. And if you are a small miner who was hashing 2-10ghz, the cost of a more expensive connection will be more than the profit you bring in making it unviable.