How is it possible in US if someone reveiced salary in Bitcoin, right on that day income become taxable?
Because you had income. Whether your paid in dollars, bitcoin, Euros, or grain doesn't matter. You received payment for services and that's taxable income.
In Europe, in Hungary only when BTC is sold and sent to a bank account it become taxable.
Different countries tax bitcoin differently, but that would be extremely strange. I've never heard of a country that had an income tax but exempted from tax income that wasn't in currency form. I guess it's possible to have a country that treats a trade of work for bitcoin as barter and only taxes barter as income if the traded asset is sold.
My tax consultant said the reason is because BTC is not an acknowledged currency at our central bank, this is the difference between EU and US BTC taxation. Do you agree?
The US doesn't treat BTC as a currency either, they treat it as a commodity or generic asset. US income tax doesn't care whether you get paid in dollars, bitcoin, or furs -- it's still taxable income as soon as there are no significant obstacles to you taking possession of it.