The UK is barred from routinely passing on details of UK criminal records under EU law. However the UK is permitted to pass on information in responses to specific requests from the USA and a great deal is passed on under the guise of 'anti-terrorism' (despite the fact the vast amount of such information almost certainly has absolutely nothing to do with potential terrorist threats).
If you apply for a tourist visa (without disclosing your conviction) you might get away with it. However if you apply for any form of work visa, or residence visa, the stringent checks that the US authorities carry out will almost certainly reveal your conviction.
Canada shares information with the USA, so anything the US authorities can find out can probably also be found out by the Canadian ones. The situation may well be similar with Australia. (Because of the security issues involved, it's almost impossible to find out exactly what is passed from one country to another but it's probably a great deal more than anyone will ever admit to).
Declaring such a recent conviction would almost certainly result in you being refused any form of visa for the countries you mention. (Canadian law places an automatic bar on you being given one, as does US law if the offence is classified as 'moral turpitude'). You typically need to allow 10 years to pass before you might be considered for a visa.