Ipad purchased in USA and bring home to use in Australia?

Your iPad will be usable when you return to Australia. Whilst Cellular models internal hardware may differ between geographic regions, sometimes supporting region specific Cellular bands, most models support the core Cellular bands used in most regions of the world.

Wireless carrier support and features for iPad - Apple Support

WiFi capabilities between devices of the same basic model are the same around the world - your iPad using only those bands which are in-use wherever you are.

Your basic Apple one-year limited warranty is valid - and will be honoured in most countries where Apple have official representation - such as Australia. Apple reserve the right to limit warranty service to that available in the country where the claim is made.

AppleCare+ coverage, if you elected to pay for this extended cover, is only valid in the country/region in which the purchase was made.

Did you buy an iPad with the cellular option? Sometimes getting cellular to work in other countries is an issue.

Other than that, there is no guarantee you'll be able to get the iPad repaired in Australia, even for a fee. iPad models are unique to each region.

~Lyssa