I would try also increasing your net buffer for the command, via a set net_buffer_length=1000000; 
Try disabling foreign key checks too, if you know the data.sql file is clean and doesn't violate any foreign key constraints.
You might get a bit more granularity if you don't try to do it all in one command and use the interactive shell instead:
mysql -u root -p database
> set global max_allowed_packet=10000000000;
ect . . .
> source data.sql;