I’d say it’s definitely obvious you’re not a native speaker; a few sounds are slightly ‘off’, but it’s mostly because of the way your accent varies so much. For example, you have the habit of dropping T’s (Bri’ish) which is common in a lot of British accents, but you pronounced “accent” at 0:26 closer to “eccent”, which is more along the lines of RP (but also something I hear in some non-native accents, specifically German). You also pronounced “out” at 1:08 with a distinct brogue. I wouldn’t have guessed Australian though, and certainly not American.

I think what happens is that people just assume you must be native because your pronunciation is so clear, regardless of whether your accent is ‘consistent’ or not. I’ve come to realize most people just aren’t good with accents, as I’m a native English speaker with a mixed accent and I, too, have had people try and place it with guesses from America and Canada, to Ireland and Australia.