Plenty. There is a section of US law, iNA214b, that says you need to prove you don’t have immigrant intent in order to be granted tourist or other non-immigrant status (whether applying for a visa, or applying for entry on either a visa or VWP). That is much harder to do when you’ve submitted a formal application to immigrate. If you feel that being Australian makes it easy enough to prove that you wont immigrate then you may feel this is not important to you. Or if you still have strong ties to Australia when you try enter the US (own a home, good job etc) that would help overcome the presumption. 214b is apparently the most common reason for visa/entry denial.